Association between the length of in vitro embryo culture, mode of ART, and the initial endogenous hCG rise in ongoing singleton pregnancies.

STUDY QUESTION: Is there an association between the length of in vitro culture, mode of ART and the initial endogenous hCG rise, in cycles with a foetal heartbeat after single embryo transfer (ET) and implantation? SUMMARY ANSWER: Both the length of in vitro culture and the mode of ART have an impact on the initial endogenous rise in hCG in singleton pregnancies. WHAT IS KNOWN ALREADY: Different factors have been identified to alter the kinetics of hCG in pregnancies. Current studies show conflicting results regarding the kinetics of hCG after different types of ART (fresh vs frozen ET (FET)), the inclusion or not of preimplantation genetic testing (PGT), and the length of time in in vitro culture. STUDY DESIGN, SIZE, DURATION: This was a multicentre cohort study, using prospectively collected data derived from 4938 women (5524 treatment cycles) undergoing IUI (cycles, n = 608) or ART (cycles, n = 4916) treatments, resulting a in singleton ongoing pregnancy verified by first-trimester ultrasound scan. Data were collected from the Danish Medical Data Centre, used by the three participating Danish public fertility clinics at Copenhagen University hospitals: Herlev Hospital, Hvidovre Hospital, and Rigshospitalet, from January 2014 to December 2021. PARTICIPANTS/MATERIALS, SETTING, METHODS: The fresh ET cycles included cleavage-stage (2 or 3 days in vitro) and blastocyst (5 days in vitro) transfers. FET cycles included cleavage-stage (3 days in vitro before cryopreservation) or blastocyst (5 or 6 days in vitro before cryopreservation) transfers. The IUI cycles represented no time in vitro. To attain a comparable interval for serum-hCG (s-hCG), the ovulation induction time was identical: 35-37 h before oocyte retrieval or IUI. The conception day was considered as: the insemination day for pregnancies conceived after IUI, the oocyte retrieval day for fresh ET, or the transfer day minus 3 or 5 as appropriate for FET of Day 3 or 5 embryos. Multiple linear regression analysis was used, including days post-conception for the hCG measurement as a covariate, and was adjusted for the women's age, the cause of infertility, and the centre. For FET, a sensitivity analysis was used to adjust for endometrial preparation. MAIN RESULTS AND THE ROLE OF CHANCE: The study totally includes 5524 cycles: 2395 FET cycles, 2521 fresh ET cycles, and 608 IUI cycles. Regarding the length of in vitro culture, with IUI as reference (for no time in in vitro culture), we found a significantly lower s-hCG in pregnancies achieved after fresh ET (cleavage-stage ET or blastocyst transfer). S-hCG was 18% (95% CI: 13-23%, P < 0.001) lower after fresh cleavage-stage ET, and 23% (95% CI: 18-28%, P < 0.001) lower after fresh blastocyst transfer compared to IUI. In FET cycles, s-hCG was significantly higher after blastocyst transfers compared to cleavage-stage FET, respectively, 26% (95% CI: 13-40%, P < 0.001) higher when cryopreserved on in vitro Day 5, and 14% (95% CI: 2-26%, P = 0.02) higher when cryopreserved on in vitro Day 6 as compared to Day 3. Regarding the ART treatment type, s-hCG after FET blastocyst transfer (Day 5 blastocysts) cycles was significantly higher, 33% (95% CI: 27-45%, P < 0.001), compared to fresh ET (Day 5 blastocyst), while there was no difference between cleavage-stage FET (Days 2 + 3) and fresh ET (Days 2 + 3). S-hCG was 12% (95% CI: 4-19%, 0.005) lower in PGT FET (Day 5 blastocysts) cycles as compared to FET cycles without PGT (Day 5 blastocysts). LIMITATIONS, REASONS FOR CAUTION: The retrospective design is a limitation which introduces the risk of possible bias and confounders such as embryo score, parity, and ovarian stimulation. WIDER IMPLICATIONS OF THE FINDINGS: This study elucidates how practices in medically assisted reproduction treatment are associated with the hCG kinetics, underlining a potential impact of in vitro culture length and mode of ART on the very early embryo development and implantation. The study provides clinicians knowledge that the type of ART used may be relevant to take into account when evaluating s-hCG for the prognosis of the pregnancy. STUDY FUNDING/COMPETING INTEREST(S): No funding was received for this study. AP has received consulting fees, research grants, or honoraria from the following companies: Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos, Merck A/S, and Organon. AZ has received grants and honoraria from Gedeon Richter. NLF has received grants from Gedeon Richter, Merck A/S, and Cryos. MLG has received honoraria fees or research grants from Gedeon Richter, Merck A/S, and Cooper Surgical. CB has received honoraria from Merck A/S. MB has received research grants and honoraria from IBSA. MPR, KM, and PVS all report no conflicts of interest. TRIAL REGISTRATION NUMBER: The study was registered and approved by the Danish Protection Agency, Capital Region, Denmark (Journal-nr.: 21019857). No approval was required from the regional ethics committee according to Danish law.

Androgen and inhibin B levels during ovarian stimulation before and after 8 weeks of low-dose hCG priming in women with low ovarian reserve.

STUDY QUESTION: Does 8 weeks of daily low-dose hCG administration affect androgen or inhibin B levels in serum and/or follicular fluid (FF) during the subsequent IVF/ICSI cycle in women with low ovarian reserve? SUMMARY ANSWER: Androgen levels in serum and FF, and inhibin B levels in serum, decreased following 8 weeks of hCG administration. WHAT IS KNOWN ALREADY: Recently, we showed that 8 weeks of low-dose hCG priming, in between two IVF/ICSI treatments in women with poor ovarian responder (anti-Müllerian hormone (AMH) <6.29 pmol/l), resulted in more follicles of 2-5 mm and less of 6-10-mm diameter at the start of stimulation and more retrieved oocytes at oocyte retrieval. The duration of stimulation and total FSH consumption was increased in the IVF/ICSI cycle after priming. Hypothetically, hCG priming stimulates intraovarian androgen synthesis causing upregulation of FSH receptors (FSHR) on granulosa cells. It was therefore unexpected that antral follicles were smaller and the stimulation time longer after hCG priming. This might indicate a different mechanism of action than previously suggested. STUDY DESIGN, SIZE, DURATION: Blood samples were drawn on stimulation day 1, stimulation days 5-6, trigger day, day of oocyte retrieval, and oocyte retrieval + 5 days in the IVF/ICSI cycles before and after hCG priming (the control and study cycles, respectively). FF was collected from the first aspirated follicle on both sides during oocyte retrieval in both cycles. The study was conducted as a prospective, paired, non-blinded, single-center study conducted between January 2021 and July 2021 at a tertiary care center. The 20 participants underwent two identical IVF/ICSI treatments: a control cycle including elective freezing of all blastocysts and a study cycle with fresh blastocyst transfer. The control and study cycles were separated by 8 weeks (two menstrual cycles) of hCG priming by daily injections of 260 IU recombinant hCG. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women aged 18-40 years with cycle lengths of 23-35 days and AMH <6.29 pmol/l were included. Control and study IVF/ICSI cycles were performed in a fixed GnRH-antagonist protocol. MAIN RESULTS AND THE ROLE OF CHANCE: Inhibin B was lower on stimulation day 1 after hCG priming (P = 0.05). Dehydroepiandrosterone sulfate (DHEAS) was significantly lower on stimulation day 1 (P = 0.03), and DHEAS and androstenedione were significantly lower on stimulation days 5-6 after priming (P = 0.02 and P = 0.02) The testosterone level in FF was significantly lower in the study cycle (P = 0.008), while the concentrations of inhibin B and androstenedione in the FF did not differ between the study and control cycles. A lower serum inhibin B in the study cycle corresponds with the antral follicles being significantly smaller after priming, and this probably led to a longer stimulation time in the study cycle. This contradicts the theory that hCG priming increases the intraovarian androgen level, which in turn causes more FSHR on developing (antral up to preovulatory) follicles. However, based on this study, we cannot rule out that an increased intra-follicular androgen level was present at initiation of the ovarian stimulation, without elevating the androgen level in serum and that an increased androgen level may have rescued some small antral follicles that would have otherwise undergone atresia by the end of the previous menstrual cycle. We retrieved significantly more oocytes in the Study cycle, and the production of estradiol per follicle ≥10-mm diameter on trigger day was comparable in the study and control cycles, suggesting that the rescued follicles were competent in terms of producing oocytes and steroid hormones. LIMITATIONS, REASONS FOR CAUTION: The sample size was small, and the study was not randomized. Our study design did not allow for the measurement and comparison of androgen levels or FSHR expression in small antral follicles before and immediately after the hCG-priming period. WIDER IMPLICATIONS OF THE FINDINGS: The results make us question the mechanism of action behind hCG priming prior to IVF. It is important to design a study with the puncture of small antral follicles before and immediately after priming to investigate the proposed hypothesis. Improved cycle outcomes, i.e. more retrieved oocytes, must be confirmed in a larger, preferably randomized study. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by an unrestricted grant from Gedeon Richter awarded to the institution. A.P. reports personal consulting fees from PregLem SA, Novo Nordisk A/S, Ferring Pharmaceuticals A/S, Gedeon Richter Nordics AB, Cryos International, and Merck A/S outside the submitted work and payment or honoraria for lectures from Gedeon Richter Nordics AB, Ferring Pharmaceuticals A/S, Merck A/S, and Theramex and Organon & Co and payment for participation in an advisory board for Preglem. Grants to the institution have been provided by Gedeon Richter Nordics AB, Ferring Pharmaceuticals A/S, and Merck A/S, and equipment and travel support has been given to the institution by Gedeon Richter Nordics AB. The remaining authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Identifier: NCT04643925.

Eight weeks of androgen priming by daily low-dose hCG injections before ICSI treatment in women with low ovarian reserve.

STUDY QUESTION: Does 8 weeks of continuous low-dose hCG administration increase the proportion of antral follicles that reach the preovulatory state during ovarian stimulation (OS) in women with low ovarian reserve? SUMMARY ANSWER: The proportion of antral follicles (2-10 mm) that reached the preovulatory state did not increase. WHAT IS KNOWN ALREADY: The administration of androgens prior to OS might upregulate FSH receptor (FSHR) expression on granulosa cells, making follicles more responsive to exogenous FSH stimulation during OS. LH and hCG stimulate the local follicular androgen synthesis in theca cells and may be used as an endogenous androgen priming method. Exogenous priming by testosterone and dehydroepiandrosterone (DHEA) have been shown to increase the number of retrieved oocytes and live birth rate but the studies are small, and their use is associated with side effects. STUDY DESIGN, SIZE, DURATION: A prospective, paired, non-blinded single-center study including 20 women serving as their own controls conducted between January 2021 and July 2021 at The University Hospital Copenhagen Rigshospitalet, Denmark. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants underwent two identical consecutive IVF/ICSI treatments, a Control cycle and a Study cycle, separated by ∼8 weeks (two menstrual cycles) of daily injections of 260 IU recombinant hCG (rhCG). A freeze-all strategy was applied in the Control cycle. Both IVF/ICSI cycles were performed in a fixed GnRH antagonist protocol using a daily dose of 300 IU recombinant FSH (rFSH) and GnRH antagonist 0.25 mg from stimulation days 5-6. MAIN RESULTS AND THE ROLE OF CHANCE: Follicular output rate, defined as the number of follicles >16 mm on hCG trigger day divided by the antral follicle count (2-10 mm) at baseline, did not increase after 8 weeks of hCG priming (P = 0.8). The mean number of oocytes retrieved was significantly higher after the hCG priming being 4.7 (2.8) vs 3.2 (1.7) in the Study and Control cycle, respectively (P = 0.01). The duration of stimulation was longer in the Study versus the Control cycle (P = 0.05), despite the use of identical hCG trigger criterion and similar diameters of the three biggest follicles on hCG trigger day in the two cycles (P = 0.9). LIMITATIONS, REASONS FOR CAUTION: The sample size was small, and the number of oocytes retrieved was not the primary endpoint. Larger studies are needed to confirm this finding. WIDER IMPLICATIONS OF THE FINDINGS: Long-term, low-dose rhCG administration may increase the number of oocytes retrieved during IVF/ICSI in women with low ovarian reserve, but more research is needed before firm conclusions can be drawn. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by an unrestricted grant from Gedeon Richter. A.P. reports personal consulting fees from PregLem SA, Novo Nordisk A/S, Ferring Pharmaceuticals A/S, Gedeon Richter Nordics AB, Cryos International, and Merck A/S outside the submitted work and payment or honoraria for lectures from Gedeon Richter Nordics AB, Ferring Pharmaceuticals A/S, Merck A/S, and Theramex and Organon & Co. Grants to the institution have been provided by Gedeon Richter Nordics AB, Ferring Pharmaceuticals A/S, and Merck A/S and receipt of equipment by the institution from Gedeon Richter Nordics AB is reported. The remaining authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Identifier: NCT04643925.

Good practice recommendations on add-ons in reproductive medicine†.

STUDY QUESTION: Which add-ons are safe and effective to be used in ART treatment? SUMMARY ANSWER: Forty-two recommendations were formulated on the use of add-ons in the diagnosis of fertility problems, the IVF laboratory and clinical management of IVF treatment. WHAT IS KNOWN ALREADY: The innovative nature of ART combined with the extremely high motivation of the patients has opened the door to the wide application of what has become known as 'add-ons' in reproductive medicine. These supplementary options are available to patients in addition to standard fertility procedures, typically incurring an additional cost. A diverse array of supplementary options is made available, encompassing tests, drugs, equipment, complementary or alternative therapies, laboratory procedures, and surgical interventions. These options share the common aim of stating to enhance pregnancy or live birth rates, mitigate the risk of miscarriage, or expedite the time to achieving pregnancy. STUDY DESIGN, SIZE, DURATION: ESHRE aimed to develop clinically relevant and evidence-based recommendations focusing on the safety and efficacy of add-ons currently used in fertility procedures in order to improve the quality of care for patients with infertility. PARTICIPANTS/MATERIALS, SETTING, METHODS: ESHRE appointed a European multidisciplinary working group consisting of practising clinicians, embryologists, and researchers who have demonstrated leadership and expertise in the care and research of infertility. Patient representatives were included in the working group. To ensure that the guidelines are evidence-based, the literature identified from a systematic search was reviewed and critically appraised. In the absence of any clear scientific evidence, recommendations were based on the professional experience and consensus of the working group. The guidelines are thus based on the best available evidence and expert agreement. Prior to publication, the guidelines were reviewed by 46 independent international reviewers. A total of 272 comments were received and incorporated where relevant. MAIN RESULTS AND THE ROLE OF CHANCE: The multidisciplinary working group formulated 42 recommendations in three sections; diagnosis and diagnostic tests, laboratory tests and interventions, and clinical management. LIMITATIONS, REASONS FOR CAUTION: Of the 42 recommendations, none could be based on high-quality evidence and only four could be based on moderate-quality evidence, implicating that 95% of the recommendations are supported only by low-quality randomized controlled trials, observational data, professional experience, or consensus of the development group. WIDER IMPLICATIONS OF THE FINDINGS: These guidelines offer valuable direction for healthcare professionals who are responsible for the care of patients undergoing ART treatment for infertility. Their purpose is to promote safe and effective ART treatment, enabling patients to make informed decisions based on realistic expectations. The guidelines aim to ensure that patients are fully informed about the various treatment options available to them and the likelihood of any additional treatment or test to improve the chance of achieving a live birth. STUDY FUNDING/COMPETING INTEREST(S): All costs relating to the development process were covered from ESHRE funds. There was no external funding of the development process or manuscript production. K.L. reports speakers fees from Merck and was part of a research study by Vitrolife (unpaid). T.E. reports consulting fees from Gynemed, speakers fees from Gynemed and is part of the scientific advisory board of Hamilton Thorne. N.P.P. reports grants from Merck Serono, Ferring Pharmaceutical, Theramex, Gedeon Richter, Organon, Roche, IBSA and Besins Healthcare, speakers fees from Merck Serono, Ferring Pharmaceutical, Theramex, Gedeon Richter, Organon, Roche, IBSA and Besins Healthcare. S.R.H. declares being managing director of Fertility Europe, a not-for-profit organization receiving financial support from ESHRE. I.S. is a scientific advisor for and has stock options from Alife Health, is co-founder of IVFvision LTD (unpaid) and received speakers' fee from the 2023 ART Young Leader Prestige workshop in China. A.P. reports grants from Gedeon Richter, Ferring Pharmaceuticals and Merck A/S, consulting fees from Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos and Merck A/S, speakers fees from Gedeon Richter, Ferring Pharmaceuticals, Merck A/S, Theramex and Organon, travel fees from Gedeon Richter. The other authors disclosed no conflicts of interest. DISCLAIMER: This Good Practice Recommendations (GPRs) document represents the views of ESHRE, which are the result of consensus between the relevant ESHRE stakeholders and are based on the scientific evidence available at the time of preparation.ESHRE GPRs should be used for information and educational purposes. They should not be interpreted as setting a standard of care or bedeemedinclusive of all proper methods of care, or be exclusive of other methods of care reasonably directed to obtaining the same results.Theydo not replace the need for application of clinical judgement to each individual presentation, or variations based on locality and facility type.Furthermore, ESHRE GPRs do not constitute or imply the endorsement, or favouring, of any of the included technologies by ESHRE.

Women with female infertility seeking medically assisted reproduction are not at increased risk of developing multiple sclerosis.

STUDY QUESTION: Is female infertility among women seeking medically assisted reproduction (MAR) associated with prevalent as well as incident multiple sclerosis (MS)? SUMMARY ANSWER: Women with a record of female infertility did not have an increased risk of developing MS compared with apparent fertile women; however, the prevalence of MS was slightly higher among women undergoing MAR compared with women who had a child without MAR, but this was not related to origin of infertility (i.e. male versus female factor infertility). WHAT IS KNOWN ALREADY: Women with MS have fewer children compared with women without MS. Persons with MS more often have other coexisting autoimmune disorders including hypothyroidism compared with the general population. Thyroid dysfunction is associated with ovarian cause of infertility, miscarriage and ovarian failure. Conversely, women with endometriosis, that is highly associated with infertility, also more often have other coexisting autoimmune diseases including MS and hypothyroidism compared with the general population. However, whether the low fertility rate among women with MS is due to a genetically predisposition to other autoimmune and endocrine disorders that leads to reduced fertility, or an active choice of the woman, disease-related pathology or treatment-specific effect on endocrine and/or ovarian function, is not completely understood. STUDY DESIGN, SIZE, DURATION: A register-based cohort study of a total of 310 357 women from 1996 to 2018. A cross-sectional design was used for analysing prevalence of MS, whereas a cohort design with up to 24 years of follow-up was used for analysing incidence of MS. PARTICIPANTS/MATERIALS, SETTING, METHODS: Three cohorts were included in the study (i) 55 404 women with a female infertility diagnosis registered in the Danish IVF register; (ii) 25 096 women with only male factor infertility recorded in the IVF register and thus no female infertility diagnosis and (iii) 229 857 age- and calendar-matched women with a record of first child birth in the Danish Medical Birth Register (DMBR) and no record ever in the IVF register. The prevalence and incidence of MS in the female infertility cohort were compared with the two control cohorts of apparent fertile women using log-binomial regression and Cox proportional hazard regression, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: The crude prevalence of having MS per 1000 persons was 3.2 for women who had undergone MAR treatment regardless of origin of infertility (i.e. male versus female factor infertility) and 2.3 for fertile DMBR controls. The age, calendar and educational level adjusted prevalence ratio of having a diagnosis of MS at the first MAR treatment was 1.27 (95% CI 1.07-1.52) for infertile women compared with fertile DMBR controls, and 1.00 (95% CI 0.77-1.31) for comparison to women with a male partner with infertility who had also undergone MAR treatment. We found no association between incident MS and female infertility compared with either of the control groups of fertile women. LIMITATIONS, REASON FOR CAUTION: The cohort of infertile women is highly selected on the basis of their choice of having fertility treatment and thus does not include women with unestablished infertility or women who, for some reason, have chosen not to have MAR treatment. Additionally, due to the nature of the observational study design, we cannot exclude the possibility of unmeasured and/or residual confounding. WIDER IMPLICATIONS OF THE FINDINGS: Our results suggest that women with MS may undergo MAR treatment more often than women without MS due to more awareness about the possibility of MAR treatments, sexual dysfunction related to MS disease, but also need for timing of the pregnancy to avoid an unnecessary long time period without disease modifying therapy-especially of high efficacy-and hence a wish to conceive quickly. These findings are important for clinicians dealing with women with MS of childbearing age. STUDY FUNDING/COMPETING INTEREST(S): The authors received no financial support for the study. T.I.K. has served on a scientific advisory board for Novartis and has received support for congress participation from Biogen. M.M. has served on scientific advisory boards for Biogen, Sanofi, Roche, Novartis, Merck, Abbvie and Alexion. She has received honoraria for lecturing from Biogen, Merck, Novartis, Sanofi and Genzyme and has received research support and support for congress participation from Biogen, Genzyme, Roche, Merck and Novartis. The remaining authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Cardiovascular function in 8- to 9-year-old singletons born after ART with frozen and fresh embryo transfer.

STUDY QUESTION: Do 8- to 9-year-old singletons conceived after frozen embryo transfer (FET) or fresh embryo transfer (Fresh-ET) have increased arterial stiffness compared to naturally conceived (NC) children? SUMMARY ANSWER: The process of FET or Fresh-ET is not associated with altered cardiovascular function in 8- to 9-year-old singletons, including arterial stiffness, as compared to NC children. WHAT IS KNOWN ALREADY: ART has been suggested to influence cardiovascular risk factors (i.e. endothelial dysfunction, increased arterial blood pressure and insulin resistance). It is not known if ART procedures alter arterial stiffness in singletons. STUDY DESIGN, SIZE, DURATION: A cohort study was carried out, including 8- to 9-year-old singletons conceived after FET, Fresh-ET and NC children (50 children in each group). This study was conducted between November 2018 and August 2020. PARTICIPANTS/MATERIALS, SETTING, METHODS: In total, 150 singletons were identified through the Danish IVF Registry and the Medical Birth Registry. They underwent cardiac magnetic resonance imaging (CMR) and anthropometric measurements. Parental data were collected using questionnaires. NC children were matched by sex and birth year with FET/Fresh-ET children. Exclusion criteria were congenital heart disease, maternal gestational diabetes or maternal diabetes mellitus. Our primary outcome was arterial stiffness, which is assessed from noninvasive arterial blood pressure and aortic ascendens distensibility. The secondary outcome was the pulse wave velocity of total aorta and exploratory outcomes were left ventricular ejection fraction, mean arterial pressure, cardiac output and total peripheral resistance. Measurements and analyses were performed blinded to the child group. MAIN RESULTS AND THE ROLE OF CHANCE: Aortic ascendens distensibility of children conceived after FET and Fresh-ET did not differ from NC children (mean (SD): FET 11.1 (3.6) 10-3 mmHg-1, Fresh-ET 11.8 (3.0) 10-3 mmHg-1, NC 11.4 (2.8) 10-3 mmHg-1, P > 0.05). Multivariate linear regression was performed to adjust for potential confounders (i.e. child sex and age, maternal BMI at early pregnancy and maternal educational level). Data showed no statistically significant differences between study groups and aortic ascendens distensibility. However, the fully adjusted model showed a non-significant tendency of lowered aortic ascendens distensibility in children born after FET compared to Fresh-ET (ß estimate (95% CI): -0.99 10-3 mmHg-1 (-2.20; 0.21)) and NC children (ß estimate (95% CI): -0.77 10-3 mmHg-1 (-1.98; 0.44)). Lastly, secondary and exploratory outcomes did not differ between the groups. Primary and secondary outcomes showed good intra-rater reliability. LIMITATIONS, REASONS FOR CAUTION: This study is possibly limited by potential selection bias as the participation rate was higher in the ART compared to the NC group. Also, in some variables, the study groups differed slightly from the non-participant population. The non-participant population (n = 1770) included those who were excluded, not invited to CMR scan, or declined to participate in this study. WIDER IMPLICATIONS OF THE FINDINGS: Our findings indicate that children born after FET or Fresh-ET do not have altered cardiovascular function, including arterial stiffness. This is reassuring for the future use of ART. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by the Novo Nordisk Foundation (grant reference number: NNF19OC0054340) and The Research Foundation of Rigshospitalet. All authors declared no conflict of interests. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT03719703.

Puberty disorders among ART-conceived singletons: a Nordic register study from the CoNARTaS group.

STUDY QUESTION: Do ART-conceived children have an increased risk for puberty disorders? SUMMARY ANSWER: Both ART-conceived boys and girls had a higher risk of puberty disorders; early puberty was more common among girls and late puberty among boys. WHAT IS KNOWN ALREADY: Some physiological differences in growth and metabolism have been reported for ART-conceived children compared to non-ART-conceived children. Knowledge on pubertal development and disorders in ART-conceived children is limited. STUDY DESIGN, SIZE, DURATION: A register-based cohort study was carried out including data from 1985 to 2015. The Committee of Nordic Assisted Reproductive Technology and Safety (CoNARTaS) study population consists of all live and stillborn children, as well as their mothers, registered in the Medical Birth Registers during the study period in Denmark, Sweden, Finland and Norway. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 122 321 ART-conceived singletons and 6 576 410 non-ART singletons born in Denmark (1994-2014), Finland (1990-2014), Norway (2002-2015) and Sweden (1985-2015) were included. Puberty disorders were defined using International Classification of Diseases and Related Health Problems (ICD)-9/ICD-10 codes and classified in the following groups: late puberty (6268/E30.0), early puberty (2591 and 2958/E30.1 and E30.8) and unspecified disorders (V212 and V579/E30.9 and Z00.3 as well as Z51.80 for Finland). The results in Cox regression were adjusted for maternal age, parity, smoking, gestational diabetes, chronic hypertension, hypertensive disorders during pregnancy and country, and further for either gestational age, birthweight, small for gestational age or large for gestational age. MAIN RESULTS AND THE ROLE OF CHANCE: There were 37 869 children with diagnoses related to puberty disorders, and 603 of them were born after ART. ART-conceived children had higher risks for early (adjusted hazard ratio (aHR) 1.45, 95% CI: 1.29-1.64) and late puberty (aHR 1.47, 95% CI: 1.21-1.77). Girls had more diagnoses related to early puberty (aHR 1.46, 95% CI: 1.29-1.66) and boys with late puberty (aHR 1.55, 95% CI: 1.24-1.95). LIMITATIONS, REASONS FOR CAUTION: Using reported puberty disorders with ICD codes in health care registers might vary, which may affect the numbers of cases found in the registers. Register data may give an underestimation both among ART and non-ART-conceived children, especially among non-ART children, who may not be as carefully followed as ART-conceived children. Adjustment for causes and duration of infertility, mothers' own puberty characteristics and BMI, as well as children's BMI, was not possible because data were not available or data were missing for the early years. It was also not possible to compare ART to non-ART siblings or to study the pubertal disorders by cause of subfertility owing to a small number of discordant sibling pairs and a large proportion of missing data on cause of subfertility. WIDER IMPLICATIONS OF THE FINDINGS: This large, register-based study suggests that ART-conceived children have a higher risk for puberty disorders. However, the mechanisms of infertility and pubertal onset are complex, and ART is a rapidly advancing field with various treatment options. Studying the pubertal disorders of ART-conceived offspring is a continuing challenge. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Nordic Trial Alliance: a pilot project jointly funded by the Nordic Council of Ministers and NordForsk (71450), the Central Norway Regional Health Authorities (46045000), the Nordic Federation of Obstetrics and Gynaecology (NF13041, NF15058, NF16026 and NF17043), the Interreg Öresund-Kattegat-Skagerrak European Regional Development Fund (ReproUnion project), the Research Council of Norway's Centre of Excellence funding scheme (262700), the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (ALFGBG-70940) and FLUX Consortium 'Family Formation in Flux-Causes, Consequences and Possible Futures', funded by the Strategic Research Council, Academy of Finland (DEMOGRAPHY 345130). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. The authors have no conflicts of interest to disclose. TRIAL REGISTRATION NUMBER: N/A.

Parenthood among men diagnosed with cancer in childhood and early adulthood: trends over time in a Danish national cohort.

STUDY QUESTION: Is the rate of fatherhood among men diagnosed with cancer in childhood and early adulthood different from men without cancer, and, if so, have the differences changed over time? SUMMARY ANSWER: Men diagnosed with cancer have had significantly reduced rates of fatherhood compared with undiagnosed men; however, the rates of fatherhood among the cancer survivors have increased markedly over time. WHAT IS KNOWN ALREADY: The number of children and young adolescents who survive cancer has steadily increased over recent decades, with a current 5-year survival rate of approximately 80%. Consequently, life circumstances after cancer have gained increasing importance, including the desire among survivors to have children and a family. ARTs to aid reproduction among cancer survivors have been developed, and fertility preservation is increasingly a topic being discussed before undergoing cancer treatment. But the potential for fertility preservation differs dependent on age at diagnosis and type of cancer. Earlier studies have shown a decreased fertility rate among survivors of child and adolescent cancer compared to those diagnosed in early adulthood. STUDY DESIGN, SIZE, DURATION: This study is a national, register-based cohort study. Men diagnosed with cancer in childhood and early adulthood (<30 years of age) were registered in the Danish Cancer Register in 1978-2016 (n = 9353). According to the time of diagnosis, each cancer-diagnosed man was randomly matched with 150 undiagnosed men from the background population within the same birth year. The men were followed until having their first child, death, migration or the end of the study (31 December 2017) in medical registers and socio-demographic population registers. PARTICIPANTS/MATERIALS, SETTING, METHODS: Fatherhood among the boys and young men diagnosed with cancer were compared with the age-matched comparison group in all statistical analyses. Cancer diagnoses were categorised as central nervous system (CNS) cancers, haematological cancers or solid cancers. Analyses were stratified by age at diagnosis (0-9, 10-19, 20-29 years) and time of diagnosis (1978-1989, 1990-1999, 2000-2009, 2010-2016). Death was incorporated as a competing risk in all analyses. MAIN RESULTS AND THE ROLE OF CHANCE: The study population consisted of 9353 boys and young men diagnosed with cancer between 1978 and 2016 and 1 386 493 men in the age-matched comparison group. Those surviving CNS cancer as young men had the lowest hazard ratio (HR) of fatherhood compared with the age-matched comparison group (HR 0.67, 95% CI 0.57-0.79), followed by survivors of haematological cancers (HR 0.90, 95% CI 0.81-1.01), while the highest chance of fatherhood was among survivors of solid cancers (HR 1.16, 95% CI 1.12-1.20) with a slightly increased HR compared with undiagnosed males. The HR of becoming a father increased over time. From the first decade to the last decade 30 years later, the HR of becoming a father increased for solid tumours (HR 0.78, 95% CI 0.73-0.83 to HR 1.08, 95% CI 0.95-1.22), haematological cancers (HR 0.64, 95% CI 0.53-0.79 to HR 0.97, 95% CI 0.73-1.30) and CNS cancers (HR 0.44, 95% CI 0.34-0.57 to HR 0.98, 95% CI 0.49-1.95) compared to the age-matched comparison group. Also, when compared with the age-matched comparison group, men diagnosed with cancer when aged 20-29 years were more likely became fathers over the time of the study (HR 0.80, 95% CI 0.74-0.86 to HR 1.08, 95% CI 0.96-1.22). LIMITATIONS, REASONS FOR CAUTION: The study was based on register data, and information was not available about the men's fertility potential, whether they had a desire to have children and whether it was possible for them to find a partner. Information about fertility preservation, e.g. sperm freezing, could also have provided additional insights. Furthermore, information about diagnosis and ART treatment would have been beneficial. WIDER IMPLICATIONS OF THE FINDINGS: Information and education of male patients diagnosed with cancer about fertility preservation options and their chances to create their own family is crucial. Reassuringly, time trends showed more men with a previous cancer diagnosis becoming fathers in recent years than in earlier years, reflecting that survival and fertility preservation have improved over time. STUDY FUNDING/COMPETING INTEREST(S): R.S. received a PhD grant from the Rosa Ebba Hansen Foundation and from the Health Foundation (J.nr. 15-B-0095). The funding for the establishment of the DANAC II Cohort was obtained from the Rosa Ebba Hansen Foundation. The authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: N/A.

Assisted reproductive technology treatment and risk of breast cancer: a population-based cohort study.

STUDY QUESTION: Is there an increased risk of breast cancer among women after ART treatment including ovarian hormone stimulation? SUMMARY ANSWER: The risk of breast cancer was slightly increased among women after ART treatment compared to age-matched, untreated women in the background population, and the risk was further increased among women initiating ART treatment when aged 40+ years. WHAT IS KNOWN ALREADY: The majority of breast cancer cases are sensitive to oestrogen, and ovarian hormone stimulation has been suggested to increase the risk of breast cancer by influencing endogenous oestrogen levels. Previous studies on ART treatment and breast cancer have varied in their findings, but several studies have small sample sizes or lack follow-up time and/or confounder adjustment. Recent childbirth, nulliparity and higher socio-economic status are breast cancer risk factors and the latter two are also associated with initiating ART treatment. STUDY DESIGN, SIZE, DURATION: The Danish National ART-Couple II (DANAC II) cohort includes women treated with ART at public and private fertility clinics in 1994-2016. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with no cancer prior to ART treatment were included (n = 61 579). Women from the background population with similar age and no prior history of ART treatment were randomly selected as comparisons (n = 579 760). The baseline mean age was 33.1 years (range 18-46 years). Results are presented as hazard ratios (HRs) with corresponding CIs. MAIN RESULTS AND THE ROLE OF CHANCE: During follow-up (median 9.69 years among ART-treated and 9.28 years among untreated), 5861 women were diagnosed with breast cancer, 695 among ART-treated and 5166 among untreated women (1.1% versus 0.9%, P < 0.0001). Using Cox regression analyses adjusted for nulliparity, educational level, partnership status, year, maternal breast cancer and age, the risk of breast cancer was slightly increased among women treated with ART (HR 1.14, 95% CI 1.12-1.16). All causes of infertility were slightly associated with breast cancer risk after ART treatment. The risk of breast cancer increased with higher age at ART treatment initiation and was highest among women initiating treatment at age 40+ years (HR 1.37, 95% CI 1.29-1.45). When comparing women with a first birth at age 40+ years with or without ART treatment, the increased risk among women treated with ART persisted (HR 1.51, 95% CI 1.09-2.08). LIMITATIONS, REASONS FOR CAUTION: Although this study is based on a large, national cohort of women, more research with sufficient power and confounder adjustment is needed, particularly in cohorts with a broad age representation. WIDER IMPLICATIONS OF THE FINDINGS: An increased risk of breast cancer associated with a higher age at ART treatment initiation has been shown. Ovarian stimulation may increase the risk of breast cancer among women initiating ART treatment when aged 40+ years. Age-related vulnerability to hormone exposure or higher hormone doses during ART treatment may explain the increased risk. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by a PhD grant to D.V. from the Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. Funding for establishing the DANAC II cohort was received from the Ebba Rosa Hansen Foundation. The authors report no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

High birth weight and large-for-gestational-age in singletons born after frozen compared to fresh embryo transfer, by gestational week: a Nordic register study from the CoNARTaS group.

STUDY QUESTION: When do the differences in birth weights become apparent between singletons born after frozen embryo transfer (FET) and fresh embryo transfer (fresh ET)? SUMMARY ANSWER: Mean birth weights after FET become significantly higher starting from gestational week (GW) 33 among boys and from GW 34 among girls. WHAT IS KNOWN ALREADY: In recent years, there has been a steep rise in recorded FET treatments, enabling widespread use of elective single embryo transfer, thus reducing the risks associated with multiple gestations. However, singletons born after FET are heavier and there is a higher risk of large-for-gestational-age (LGA) (birth weight > 90 percentiles) compared to fresh ET. In contrast, risk of small-for-gestational-age (SGA, birth weight < 10 percentiles) is lower in singletons born after FET compared to fresh ET. The reasons, timing and consequences of these differences remain largely unclear. There is limited evidence about whether this difference in growth develops before the last trimester of pregnancy. STUDY DESIGN, SIZE, DURATION: This retrospective Nordic register-based cohort study compared singletons born after FET (n = 17 500) to singletons born after fresh ET (n = 69 510) and natural conception (NC, n = 3 311 588). All live born singletons born between the years 2000 and 2015 in Denmark, Norway and Sweden at gestational age ≥22 weeks were included from the population-based Committee of Nordic ART and Safety (CoNARTaS) study population. PARTICIPANTS/MATERIALS, SETTING, METHODS: Children born after FET were compared to those born after fresh ET and NC for mean birth weight and proportion of LGA and SGA for each GW at birth. Chi-square test and tests for relative proportions were used to compare categorical variables and Student's t-test was used to compare continuous variables. Adjusted odds ratios (aORs) for LGA and SGA were calculated using logistic regressions, adjusting for year of birth, maternal age, parity, BMI, chronic hypertension, diabetes, smoking and offspring sex. MAIN RESULTS AND THE ROLE OF CHANCE: Mean birth weights were significantly higher after FET compared to fresh ET starting from GW 33 (range from 75 g to 228 g by week) for boys and starting from GW 34 (range from 90 g to 236 g by week) for girls. Boys born after FET had a significantly higher proportion of LGA (11.0-15.1%) at birth between GW 36 and 42, compared to those born after fresh ET (7.1-9.4%) (range from P < 0.001 to P = 0.048 by week). For girls born after FET, the difference was seen between GW 37 and 42 (10.6-13.4%) compared to those born after fresh ET (6.6-8.0%) (range from P < 0.001 to P = 0.009 by week).The proportion of SGA was significantly lower among boys born after FET (7.6-8.7%) compared to fresh ET (11.9-13.6%) between GW 36 and 42 (range from P < 0.001 to P = 0.016 by week). For girls born after FET, the difference was seen between GW 38 and 42 (7.0-9.3%) compared to those born after fresh ET (13.0-14.6%) (P < 0.001). The proportion of LGA (12.3-15.1%) was significantly higher for boys born after FET between GW 38 and 41 (P < 0.001) and for girls born after FET (12.6-13.4%) between GW 37 and 40 (range from P < 0.001 to P = 0.018 by week), compared to naturally conceived boys (9.7-9.9%) and girls (9.0-10.0%). All singletons born after FET had a higher risk of LGA compared to singletons born after fresh ET (aOR 1.87, 95% CI 1.76-1.98) and singletons born after NC (aOR 1.28, 95% CI 1.22-1.35). LIMITATIONS, REASONS FOR CAUTION: There may be residual confounding factors that we were not able to control for, most importantly the causes of preterm birth, which may also influence foetal growth. A further limitation is that we have no knowledge on growth patterns between implantation and GW 22. Finally, the number of children born extremely preterm or post-term was limited even in this large study population. WIDER IMPLICATIONS OF THE FINDINGS: This is, to date, the largest study on birth weights among preterm and term ART singletons with a population-based design and NC control group. The results suggest that the freeze-thaw process is associated with higher birthweights and greater risk of LGA at least in the last trimester of pregnancy. This is an important aspect of the safety profile of ART. More research is needed on the long-term outcome of these children. STUDY FUNDING/COMPETING INTEREST(S): The CoNARTaS collaboration has received the following funding: the Nordic Trial Alliance: a pilot project jointly funded by the Nordic Council of Ministers and NordForsk [71450], the Central Norway Regional Health Authorities [46045000], the Norwegian Cancer Society [182356-2016], the Nordic Federation of Obstetrics and Gynaecology [NF13041, NF15058, NF16026 and NF17043], the Interreg Öresund-Kattegat-Skagerrak European Regional Development Fund (ReproUnion project) and the Research Council of Norway's Centre of Excellence funding scheme [262700]. None of the authors have any competing interests to declare. TRIAL REGISTRATION NUMBER: ISRCTN11780826.

Type 1 diabetes in children born after assisted reproductive technology: a register-based national cohort study.

STUDY QUESTION: Do children born after assisted reproductive technology (ART) have an increased risk of developing type 1 diabetes? SUMMARY ANSWER: Children born after ART were found to have an increased risk of type 1 diabetes in the unadjusted analysis, while after adjustment this association was only significant in children born after frozen embryo transfer. WHAT IS KNOWN ALREADY?: Some studies raise concerns as to whether fertility treatments may influence long-term morbidity in children born after ART. Elevated blood pressure and altered glucose metabolism have been found after ART in a few studies. STUDY DESIGN, SIZE, DURATION: A register-based national cohort study that included all children born in Sweden between 1985 and 2015-in total, 3 138 540 children-was carried out. PARTICIPANTS/MATERIAL, SETTING, METHODS: The study was population-based and all live-born singleton children born after ART (n = 47 938) or spontaneous conception (SC) (n = 3 090 602) were included. The ART cohort comprised 36 727 children born after fresh embryo transfer and 11 211 children born after frozen embryo transfer. Several national registries were used together with data from Statistics Sweden. MAIN RESULTS AND THE ROLE OF CHANCE: In total, 202 children born after ART and 17 916 children born after SC developed type 1 diabetes, corresponding to 43.4 and 35.5 per 100 000 person-years at risk (hazard ratio [HR] 1.23; 95% confidence interval [CI], 1.07 to 1.42). Mean follow-up was 9.7 (SD 6.4) years for ART children and 16.3 (SD 9.2) years for SC children. After adjustment for calendar year of birth, HR for type 1 diabetes was 1.13; 95% CI, 0.98-1.30. After further adjustment for sex, maternal age, country of birth, educational level, smoking and parental diabetes, HR was 1.07; 95% CI, 0.93-1.23. In subgroup analyses, an association was found between frozen embryo transfer and type 1 diabetes (adjusted HR 1.52; 95% CI, 1.08-2.14 and 1.41; 95% CI, 1.05-1.89 for frozen versus fresh and frozen versus SC, respectively). When comparing intracytoplasmic sperm injection to in vitro fertilization, no difference was found (adjusted HR 1.08; 95% CI, 0.77-1.51). LIMITATIONS, REASONS FOR CAUTION: Limitations were the missing data and residual confounding caused by unknown confounders. Furthermore, the control group consisted of all children not conceived by ART and not non-ART children from subfertile mothers. The study was also performed in only singletons and not in the total ART population. WIDER IMPLICATIONS OF THE FINDINGS: Type 1 diabetes is a serious disease, affecting human life in several ways, including risk of serious complications, reduced life span and a life-long treatment. Our results are generally reassuring, showing no increase in diabetes in ART children compared to children born after SC after adjustment for relevant confounders. The observation of an association between children born after frozen embryo transfer and type 1 diabetes, although based on subgroup analyses with a limited number of children and modest in size, is however a reason for concern. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by Nordforsk 71450, the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement 70940, and the Hjalmar Svensson Foundation. The authors have no competing interests. TRIAL REGISTRATION NUMBER: ISRCTN 11780826.

Imprinting disorders in children born after ART: a Nordic study from the CoNARTaS group.

STUDY QUESTION: Is the risk of imprinting disorders increased in children conceived after ART? SUMMARY ANSWER: We found an adjusted odds ratio (AOR) of 2.84 [95% CI: 1.34-6.01] for Beckwith-Wiedemann syndrome in ART children, while the risk of Prader-Willi syndrome, Silver-Russell syndrome or Angelman syndrome was not increased in children conceived after ART. WHAT IS KNOWN ALREADY: Earlier studies, most of them small, have suggested an association between ART and imprinting disorders. STUDY DESIGN, SIZE, DURATION: This was a binational register-based cohort study. All children conceived by ART in Denmark (n = 45 393, born between 1994 and 2014) and in Finland (n = 29 244, born between 1990 and 2014) were identified. The full background populations born during the same time periods in the two countries were included as controls. Odds ratios of imprinting disorders in ART children compared with naturally conceived (NC) children were calculated. The median follow-up time was 8 years and 9 months for ART children and 11 years and 9 months for NC children. PARTICIPANTS/MATERIALS, SETTING, METHODS: From the national health registries in Denmark and Finland, we identified all children diagnosed with Prader-Willi syndrome (n = 143), Silver-Russell syndrome (n = 69), Beckwith-Wiedemann syndrome (n = 105) and Angelman syndrome (n = 72) born between 1994/1990 and 2014, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: We identified a total of 388 children diagnosed with imprinting disorders; 16 of these were conceived after ART. The overall AOR for the four imprinting disorders in ART children compared with NC children was 1.35 [95% CI: 0.80-2.29], but since eight ART children were diagnosed with Beckwith-Wiedemann syndrome, the AOR for this specific imprinting disorder was 2.84 [95% CI: 1.34-6.01]. The absolute risk of Beckwith-Wiedemann syndrome in children conceived after ART was still low: 10.7 out of 100 000 newborns. The risks of Prader-Willi syndrome, Silver-Russell syndrome and Angelman syndrome were not increased in children conceived after ART. LIMITATIONS, REASONS FOR CAUTION: Imprinting disorders are rare events and our results are based on few ART children with imprinting disorders. The aetiology is complex and only partly clarified, and the clinical diagnoses are challenged by a broad phenotypic spectrum. WIDER IMPLICATIONS OF THE FINDINGS: In the existing studies, results on the risk of imprinting disorders in children conceived after ART are ambiguous. This study adds that the risk of imprinting disorders in ART children is very small and perhaps restricted to Beckwith-Wiedemann syndrome. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Nordic Trial Alliance: a pilot project jointly funded by the Nordic Council of Ministers and NordForsk (grant number: 71450), the Nordic Federation of Obstetrics and Gynecology (grant numbers: NF13041, NF15058, NF16026 and NF17043) and the Interreg Öresund-Kattegat-Skagerak European Regional Development Fund (ReproUnion project). The authors have no conflicts of interest related to this work. TRIAL REGISTRATION NUMBER: N/A.

Obstetric and perinatal risks in 4601 singletons and 884 twins conceived after fresh blastocyst transfers: a Nordic study from the CoNARTaS group.

STUDY QUESTION: Are obstetric and perinatal outcomes in pregnancies after fresh blastocyst transfer (BT) comparable with those born after fresh cleavage stage transfer (CT) and spontaneous conception (SC)? SUMMARY ANSWER: Fresh BT is associated with a higher risk of placental and perinatal complications. WHAT IS KNOWN ALREADY: BT optimizes the selection of top-quality embryos and increases pregnancy and live birth rates per transfer compared to CT. However, concerns have been raised as extended culture duration may increase obstetric complications and impair perinatal outcomes. Previous studies have shown a higher risk of preterm birth (PTB) among infants born after BT compared with CT. Pregnancies after BT are also prone to a higher risk of same-sex twins after single embryo transfer (SET). STUDY DESIGN, SIZE, DURATION: A retrospective register-based cohort study used data from Denmark, Norway and Sweden including three cohorts: 56 557 singletons and 16 315 twins born after fresh IVF/ICSI cycles and 2 808 323 SC singletons in Denmark (birth years 1997-2014), Norway (2010-2015) and Sweden (2002-2015). Of the fresh IVF/ICSI singletons, 4601 were born after BT and 51 956 after CT. The twin cohort consisted of 884 fresh IVF/ICSI children born after BT and 15 431 fresh IVF/ICSI children born after CT. PARTICIPANTS/MATERIALS, SETTING, METHODS: Data were obtained from a large Nordic cohort of children born after ART and SC initiated by the Committee of Nordic ART and Safety (CoNARTaS). The CoNARTaS cohort was established by cross-linking National ART-, Medical Birth-, and National Patients Registers using the unique personal identification number, allocated to every citizen in the Nordic countries. Obstetric and perinatal outcomes after BT, CT and SC were compared using logistic regression analysis. For perinatal outcomes, we calculated gestational age based on the date of oocyte pick-up (OPU) and in sensitivity analyses on data from Denmark and Norway, we also calculated gestational age based on the second-trimester ultrasonography (US) scan. Risk of pregnancies with same-sex twins after SET was used as a proxy for risk of monozygotic twins. Adjustments were made for child's sex, birth year, parity (0 or >1), maternal age, body mass index, smoking, educational level, fertilization method (IVF/ICSI), the number of aspirated oocytes, SET and country. Information on educational level and the number of aspirated oocytes was not available for Norway. Children born after frozen embryo transfer were not included. The birth cohorts were restricted according to the year in which BT was introduced in the different countries. MAIN RESULTS AND THE ROLE OF CHANCE: A higher risk of placenta previa was found in singleton pregnancies after BT compared with CT (adjusted odds ratio [aOR] 2.11 [95% CI 1.76; 2.52]). Singletons born after BT had a higher risk of PTB (aOR 1.14 [95% CI 1.01; 1.29]) compared with CT singletons, when estimated based on OPU. Furthermore, an altered male/female ratio (aOR 1.13 [95% CI 1.06; 1.21]) with more males following BT compared with CT was seen. Risk of same-sex twins after SET was higher after single BT compared with single CT (aOR 1.94 [95% CI 1.42; 2.60]). LIMITATIONS, REASONS FOR CAUTION: Residual confounding cannot be excluded, in particular related to duration and cause of infertility that we could not adjust for due to lack of reliable data. WIDER IMPLICATIONS OF THE FINDINGS: Extended embryo culture to the blastocyst stage has the potential to compromise obstetric and perinatal outcomes in fresh cycles. These results are important since an increasing number of IVF/ICSI treatments are performed as BT. STUDY FUNDING/COMPETING INTEREST(S): NORDFORSK (project no: 71450). The Research Fund of Rigshospitalet, Copenhagen University Hospital. ReproUnion Collaborative study, co-financed by the European Union, Interreg V ÖKS. Grants from Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (LUA/ALF 70940), Hjalmar Svensson Research Foundation. The Research Council of Norway through its Centres of Excellence funding scheme, project number 262700. None of the authors has any conflicts of interests to declare regarding this study. TRIAL REGISTRATION NUMBER: ISRCTN11780826.

Magnesium sulphate for fetal neuroprotection at imminent risk for preterm delivery: a systematic review with meta-analysis and trial sequential analysis.

BACKGROUND: Ordinary meta-analyses indicate that magnesium sulphate (MgSO4 ) treatment in women at imminent risk for preterm delivery decreases the offspring's risk of cerebral palsy (CP). However, repetitive testing of cumulative data calls for statistical caution, e.g. by trial sequential analysis (TSA), for which there are previously insufficient samples to draw a firm conclusion. Recently, a randomised controlled trial (RCT) provided additional data that potentially increased the sample size such that a new TSA might detect a statistically significant effect. OBJECTIVES: To assess the possible fetal neuroprotective effect of MgSO4 for women at imminent risk for preterm delivery in an updated systematic review with meta-analysis and TSA. SEARCH STRATEGY: We searched MEDLINE, Embase, Cochrane and ClinicalTrials.gov on 8 October 2019. The search strategy clustered terms describing the MgSO4 intervention and preterm delivery. SELECTION CRITERIA: RCTs. DATA COLLECTION AND ANALYSIS: Two reviewers extracted the data. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using fixed-effects models. A TSA was applied to the primary outcome, CP. The quality of the evidence was assessed using GRADE. The protocol was registered in PROSPERO (registration: CRD42019151441). MAIN RESULTS: We identified six eligible trials (5917 women). MgSO4 intervention in women at imminent risk for preterm birth decreased the offspring's CP risk (meta-analysis RR 0.68, 95% CI 0.54-0.85; TSA RR 0.69, 95% CI 0.48-0.97). CONCLUSIONS: This systematic review with meta-analysis and TSA shows conclusively that MgSO4 , when given to women at imminent risk for preterm delivery, decreases the offspring's CP risk. TWEETABLE ABSTRACT: Antenatal magnesium sulphate decreases the risk of cerebral palsy in children born preterm.

Antenatal magnesium sulphate for the prevention of cerebral palsy in infants born preterm: a double-blind, randomised, placebo-controlled, multi-centre trial.

OBJECTIVE: To study the effect of antenatal magnesium sulphate (MgSO4 ) on cerebral palsy (CP) in a manner that also provides adequate power for a linked trial sequential analysis. DESIGN: Double-blind, randomised, placebo-controlled, multi-centre trial. SETTING: Fourteen Danish obstetric departments. POPULATION: In total, 560 pregnant women at risk for preterm delivery before 32 weeks of gestation were randomised from December 2011 to January 2018. Those women gave birth to 680 children. METHODS: Women were randomised to receive either a loading dose of 5 g MgSO4 followed by 1 g/hour or a placebo in identical volumes. The children were followed up at a corrected age of 18 months or older with a review of their medical charts and with the Ages and Stages Questionnaire. MAIN OUTCOME MEASURE: The primary outcome measure was moderate to severe CP. Secondary outcomes included mortality, neonatal morbidity, blindness and mild CP. RESULTS: The crude rates of moderate to severe CP in the MgSO4 group and the placebo group were 2.0% and 3.3%, respectively. The adjusted odds of moderate to severe CP were lower in the MgSO4 group than in the placebo group (odds ratio 0.61; 95% CI 0.23-1.65). CONCLUSIONS: Antenatal MgSO4 before 32 weeks of gestation decreases the likelihood of moderate to severe CP; these results are entirely consistent with other randomised evidence summarised in the linked trial sequential analysis. TWEETABLE ABSTRACT: Antenatal magnesium sulphate may decrease the risk of moderate to severe cerebral palsy in children born before 32 weeks of gestation.

Rare genetic variants suggest dysregulation of signaling pathways in low- and high-risk patients developing severe ovarian hyperstimulation syndrome.

PURPOSE: To investigate if rare gene variants in women with severe ovarian hyperstimulation syndrome (OHSS) provide clues to the mechanisms involved in the syndrome. METHODS: Among participants in a prospective randomized study (Toftager et al. 2016), six women with predicted low and six women with predicted high risk of OHSS developing severe OHSS (grades 4 and 5, Golan classification) were selected. In the same cohort, six plus six matched controls developing no signs of OHSS (Golan grade 0) were selected. Whole-exome sequencing was performed. Analysis using a predefined in silico OHSS gene panel, variant filtering, and pathway analyses was done. RESULTS: We found no convincing monogenetic association with the development of OHSS using the in silico gene panel. Pathway analysis of OHSS variant lists showed substantial overlap in highly enriched top pathways (p value range p < 0.0001 and p > 9.8E-17) between the low- and high-risk group developing severe OHSS, i.e., "the integrin-linked kinase (ILK) signaling pathway" and the "axonal guidance signaling pathway," both being connected to vasoactive endothelial growth factor (VEGF) and endothelial function. CONCLUSION: Rare variants in OHSS cases with two distinct risk profiles enrich the same signaling pathways linked to VEGF and endothelial function. Clarification of the mechanism as well as potentially defining genetic predisposition of the high vascular permeability is important for future targeted treatment and prevention of OHSS; the potential roles of ILK signaling and the axonal guidance signaling need to be validated by functional studies.

Assisted reproductive technology treatment and risk of ovarian cancer-a nationwide population-based cohort study.

STUDY QUESTION: Does hormone stimulation during assisted reproductive technology (ART) treatment increase the risk of ovarian cancer? SUMMARY ANSWER: No increased risk of ovarian cancer was found among ART-treated women, with the exception of ART-treated women with endometriosis. WHAT IS KNOWN ALREADY: Previous studies on the association between ovarian stimulation during ART and ovarian cancer have shown conflicting results. The risk of ovarian cancer varies according to the cause of infertility, and only a few studies on ART treatment and risk of ovarian cancer have had sufficient data to address this issue. Endometriosis has been linked to an increased risk of ovarian cancer. STUDY DESIGN, SIZE, DURATION: Women undergoing ART treatment during 1994-2015 were registered in the Danish IVF register. Data were linked with data from the Danish Cancer Register and socio-demographic population registers using an individual person identification number assigned to people residing in Denmark. PARTICIPANTS/MATERIALS, SETTING, METHODS: All women undergoing ART treatment were age-matched with a random sample of the female background population and followed for up to 22 years. After relevant exclusions, the population consisted of 58 472 ART-treated women and 625 330 untreated women, all with no previous malignancies. Ovarian cancer risk was assessed using multivariable cox regression analyses with adjustment for educational level, marital status, parity and treatment year. Results are shown as hazard ratios (HRs) with corresponding CIs. MAIN RESULTS AND THE ROLE OF CHANCE: In total, 393 (0.06%) women were diagnosed with ovarian cancer during follow-up (mean 9.7 years). Women treated with ART had an increased risk of ovarian cancer (HR 1.20, 95% CI 1.10-1.31), which diminished over time. The increased risk was apparent among women with female factor infertility (HR 1.36, 95% CI 1.25-1.48), whereas no female factor infertility was associated with a lower risk (HR 0.87, 95% CI 0.76-1.00). The risk was increased among women with endometriosis (HR 3.78, 95% CI 2.45-5.84), whereas no increased risk was found among ART-treated women with polycystic ovary syndrome, other female causes of infertility and unexplained infertility. LIMITATIONS, REASONS FOR CAUTION: The association between ART treatment and ovarian cancer is likely influenced by increased detection due to multiple ultrasound scans during ART treatment. WIDER IMPLICATIONS OF THE FINDINGS: Undergoing ART treatment without the presence of endometriosis was not associated with an increased risk of ovarian cancer, which is reassuring. Whether ART treatment increases the risk of ovarian cancer among women with endometriosis needs further investigation. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by a PhD grant to D.V. from the Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. Funding for establishing the Danish National ART-couple II cohort was achieved from Ebba Rosa Hansen Foundation. The funders had no influence on data collection, analyses or results presented. The authors have no conflicts of interest to declare.

Patients' attitudes and preferences towards a freeze-all strategy in ART treatment.

STUDY QUESTION: What are the attitudes towards different aspects of a freeze-all strategy and elective frozen embryo transfer (eFET) in comparison with fresh embryo transfer in assisted reproductive technology treatment among female and male patients before and after their first ART treatment cycle in a public health care setting? SUMMARY ANSWER: Despite concerns about the delay in embryo transfer associated with eFET, nearly 60% of the participants were in favor of eFET compared with fresh embryo transfer assuming that the clinical pregnancy rate was equivalent. WHAT IS KNOWN ALREADY: Vitrification and blastocyst transfer have considerably improved success rates after FET with ongoing pregnancy rates in frozen cycles approaching those seen in fresh treatment cycles. Furthermore, the risk of ovarian hyperstimulation syndrome (OHSS) is essentially eliminated in FET cycles, and FET may be beneficial to the endometrial and fetal development because a hormonal environment mirroring the natural cycle is enabled. However, the freeze-all strategy is not yet implemented as standard care. One reason is the presumption of negative patient attitudes towards a freeze-all embryo strategy. So far, no data regarding patients' attitudes on a freeze-all strategy have been published. STUDY DESIGN, SIZE, DURATION: This study was designed as a descriptive cross-sectional study including 165 fertility patients referred for their first ART treatment from December 2014 to June 2016. PARTICIPANTS/MATERIALS, SETTING, METHODS: All newly referred patients participating in a mandatory meeting before initiating ART treatment at the Fertility Clinic, Hvidovre Hospital, Copenhagen, Denmark were requested to fill in an online web-based questionnaire separately for men and women covering attitudes towards a freeze-all strategy, socio-demographic data and reproductive history. The patients were informed about both conventional fresh embryo transfer strategy and the freeze-all strategy prior to answering the questionnaire. MAIN RESULTS AND THE ROLE OF CHANCE: The total response rate was 77.1% (n = 165), and for women and men respectively 85.8 versus 66.0%. The female respondents were significantly more likely to consider the postponement of embryo transfer difficult compared to the male population (78.6 versus 35.5%; P < 0.001) and they were significantly more willing to accept a risk in treatment on own health to achieve a pregnancy than were the male respondents on their partners health (82.5 versus 96.8%; P = 0.025). However, 59.2% of the women and 59.7% of the men agreed that they would choose eFET over fresh embryo transfer if the chance of pregnancy were the same. Most of the patients furthermore agreed that the health of the mother and their baby was of highest importance. In the adjusted analyses we found no significant predictive factors for preferences towards a freeze-all strategy apart from a negative attitude towards delay of transfer in case of previous unsuccessful ART attempts. LIMITATIONS, REASONS FOR CAUTION: Selection bias cannot be excluded, as the total response rate was 77.1%. The hypothetical nature of the items may furthermore limit the validity of the results. In addition, the participants were from a single Fertility Clinic in the Capital Region of Denmark and may therefore not be representative for all fertility patients. WIDER IMPLICATIONS OF THE FINDINGS: In a clinical setting with similar pregnancy rates for eFET and fresh embryo transfer, these results indicate that patients, when given access to information on advantages and disadvantages of both fresh embryo transfer and eFET, are less prone to opt for fresh embryo transfer. This may be ground breaking for a patient-centered paradigm shift in routine ART treatment with a wider implementation of a freeze-all and eFET-strategy eliminating the risk of OHSS. STUDY FUNDING/COMPETING INTEREST(S): The Danish Council for Independent Research and Merck Serono supported the study. The study is part of the Reprounion Collaborative study, co-financed by the European Union, Interreg V ÖKS. No competing interests exist.

Cumulative live birth rate prognosis based on the number of aspirated oocytes in previous ART cycles.

STUDY QUESTION: Is the number of aspirated oocytes in the first ART cycle associated with the cumulative live birthrates (CLBR) in subsequent cycles? SUMMARY ANSWER: The number of aspirated oocytes in the first cycle was associated with CLBR in subsequent cycles. Previous treatment response predicts outcome in future cycles. WHAT IS KNOWN ALREADY: Previous reports have shown a positive association between the number of retrieved oocytes and live birthrate per fresh treatment cycle. This has also been shown for the CLBR in one complete ART-cycle, including possible subsequent frozen-thawed transfers (FER). It has been shown that women with less than five oocytes in the first cycle have poorer outcome within six complete cycles than women with more than 12 oocytes, suggesting that the number of aspirated oocytes in the first cycle may be reproduced in later cycles. However, other studies have shown that an initial low treatment response may be improved with increased gonadotrophin start-dose. STUDY DESIGN, SIZE, DURATION: The Danish National IVF-registry includes all ART treatments in public and private clinics since 1994. Treatment-cycles were cross-linked with the Medical Birth Registry, identifying treatment-related births and natural conception births. This national cohort study includes all women starting ART treatments with homologous eggs between 2002 and 2011, N = 30 486. Subjects were followed for up to four fresh ART-cycles including subsequent FER-cycles (=four complete cycles), until the first livebirth, or until December 2011. PARTICIPANTS/MATERIALS, SETTING, METHODS: The CLBR within 1-4 complete ART-cycles were calculated as the proportion of women with a livebirth, out of all women initiating ART-treatment, including drop-outs (no livebirth or no continued treatment within follow-up). In women with one year follow-up from last treatment, multivariate logistic regression analysis assessed impact of retrieved oocytes on CLBR, adjusting results for female age and cause of infertility. Hospital admission due to ovarian hyperstimulation syndrome (OHSS) was reported. MAIN RESULTS AND THE ROLE OF CHANCE: After one, two and three complete ART-cycles, the CLBRs attributable to ART treatment were 26.4% [95%CI 25.9-26.9], 42.6% [42.0-43.1] and 51.3% [50.7-51.9], respectively. The CLBR attributable to non-ART related conception (natural conception or intrauterine insemination) were 5.3% [5.0-5.6], 8.3% [8.0-8.7] and 10.6% [10.3-11.0], after one, two and three complete cycles. In women without a live birth in the first complete cycle, the number of aspirated oocytes predicted the outcome in the second and third cycle: When compared to women with 0-3 aspirated oocytes in the first cycle, the odds for live birth in the second and third cycle was 1.18 [1.07-1.30] for women with 4-9 aspirated oocytes in the first cycle, 1.41 [1.27-1.57] for women with 10-15 aspirated oocytes and 1.63 [1.42-1.88] for women with more than 15 aspirated oocytes. For women without a livebirth in the first and second cycle, the sum of aspirated oocytes predicted outcome in the third complete cycle. Women with a sum larger than six aspirated oocytes, had marked increased odds ratios for livebirth in the third complete cycle, compared to women with a sum of 0-6 oocytes in the first and second fresh cycle. Incidence of hospital-admission due to OHSS was 1.7% in the first cycle, decreasing to 1.3% and 1.0% in the second and third cycles. LIMITATIONS, REASONS FOR CAUTION: Although mandatory, there may be treatment-cycles not registered in the IVF-registry. Missing information in number of aspirated oocytes are most likely random losses of information. There were few observations in women with more than 15 aspirated oocytes and these birthrates should be interpreted cautiously. Information on gonadotrophin dose used for stimulation was not available, nor was information on dose adjustments in subsequent cycles. WIDER IMPLICATIONS OF THE FINDINGS: With these results we can counsel couples returning for fertility treatments, providing an age-stratified revised prognosis for chances of live birth and risk of OHSS, reflecting prior failed attempts and previous ovarian response. STUDY FUNDING/COMPETING INTEREST(S): This study was unconditionally funded by Ferring Pharmaceuticals and ReproUnion. The funders had no role in the study design, data collection and interpretation, or decision to submit the work for publication. The authors have no conflicts of interest. TRIAL REGISTRATION NUMBER: The study was approved by the Danish Data Protection Agency (J.nr. 2012-41-1330).

Prediction of the lower serum anti-Müllerian hormone threshold for ovarian stimulation prior to in-vitro fertilization using the Elecsys® AMH assay: a prospective observational study.

BACKGROUND: In assisted reproductive technology, prediction of treatment failure remains a great challenge. The development of more sensitive assays for measuring anti-Müllerian hormone (AMH) has allowed for the possibility to investigate if a lower threshold of AMH can be established predicting very limited or no response to maximal ovarian stimulation. METHODS: A prospective observational multicenter study of 107 women, < 40 years of age with regular menstrual cycle and serum AMH levels ≤ 12 pmol/L, treated with 300 IU/day of HP-hMG in a GnRH-antagonist protocol. AMH was measured before treatment start using the Elecsys® AMH assay by Roche Diagnostics. The ability of AMH to predict follicular development and ovarian response was assessed by receiver operating characteristics (ROC). Furthermore, the relationship between AMH at start of stimulation and cycle outcome was investigated using multivariate logistic regression analysis. RESULTS: Five out of 107 cycles (4.7%) were cancelled due to lack of follicular development and 60/107 (56%) women did not reach the classical hCG criteria for ovulation induction (≥ 3 follicles of ≥17 mm). An AMH threshold of 4 pmol/L predicted failure to reach the classical hCG criteria with 89% specificity and 53% sensitivity and an area under the curve (AUC) of 0.76 (95% CI 0.66-0.85). AMH predicted cycle cancellation due to lack of follicular development, using a cut-off value of 1.5 pmol/L, with a specificity of 96% and sensitivity of 80% (AUC = 0.92, 95% CI 0.79-1.00). A single-unit increase in AMH was associated with a 29% decrease in odds of failure to reach the classical hCG criteria (OR 0.71 95% CI 0.59-0.85, p < 0.01). The lowest AMH value compatible with a live birth was 1.3 pmol/L. CONCLUSIONS: Among women with a limited ovarian reserve, pre-treatment serum AMH levels significantly predicted failure to reach the classical hCG triggering criteria and predicted lack of follicular development using a new sensitive assay, but AMH was not suitable for withholding fertility treatment, as even very low levels were associated with live births. TRIAL REGISTRATION: Not relevant.