Growth of singletons born after frozen embryo transfer until early adulthood: a Finnish register study.

STUDY QUESTION: Are there growth differences between singleton children born after frozen embryo transfer (FET), fresh embryo transfer (ET), and natural conception (NC)? SUMMARY ANSWER: Adolescent boys born after FET have a higher mean proportion and increased odds of overweight compared to those born after fresh ET. WHAT IS KNOWN ALREADY: Children born after FET have higher mean birthweights and an increased risk of large-for-gestational-age compared to those born after fresh ET and even NC. This raises questions about possible growth differences later in childhood. Previous studies on child growth after FET report partly conflicting results and lack long-term data until adolescence. STUDY DESIGN, SIZE, DURATION: This was a cohort study based on national population-based registers, the Finnish Medical Birth Register and the Register of Primary Health Care visits, including singletons born after FET (n = 1825), fresh ET (n = 2933), and NC (n = 31 136) in Finland between the years 1995 and 2006. PARTICIPANTS/MATERIALS, SETTING, METHODS: The proportions of overweight (i.e. age- and sex-adjusted ISO-BMI for children ≥ 25) were compared between the groups. Odds ratios (ORs) and adjusted odds ratios (aORs) of overweight were calculated. Adjustments were made for birth year, preterm birth, maternal age, parity, and socioeconomic status. Mean heights, weights, and BMIs were compared between the groups each year between the ages of 7 and 18. MAIN RESULTS AND THE ROLE OF CHANCE: FET boys had a higher mean proportion of overweight (28%) compared to fresh ET (22%, P < 0.001) and NC (26%, P = 0.014) boys. For all ages combined, the aOR of overweight was increased (1.14, 95% CI 1.02-1.27) for FET boys compared to fresh ET boys. For girls, the mean proportions of overweight were 18%, 19%, and 22% for those born after FET, fresh ET, and NC, respectively (P = 0.169 for FET vs fresh ET, P < 0.001 for FET vs NC). For all ages combined, FET girls had a decreased aOR of overweight (0.89, 95% CI 0.80-0.99) compared to NC girls. Growth measurements were available for 6.9% to 30.6% of FET boys and for 4.7% to 29.4% of FET girls at different ages. LIMITATIONS, REASONS FOR CAUTION: Unfortunately, we were not able to adjust for parental anthropometric characteristics. The growth data were not available for the whole cohort, and the proportion of children with available measurements was limited at the start and end of the follow-up. During the study period, mainly cleavage stage embryos were transferred, and slow freezing was used for ART. WIDER IMPLICATIONS OF THE FINDINGS: The risk of overweight among FET boys warrants further research. Future studies should aim to investigate the mechanisms that explain this sex-specific finding and combine growth data with long-term health data to explore the possible risks of overweight and cardiometabolic disease in adulthood. STUDY FUNDING/COMPETING INTEREST(S): Funding was obtained from the Päivikki and Sakari Sohlberg Foundation, the Alma and K.A. Snellman Foundation (personal grants to A.M.T.), and the Finnish Government Research Funding. The funding sources were not involved in the planning or execution of the study. The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

Health of singletons born after frozen embryo transfer until early adulthood: a Finnish register study.

STUDY QUESTION: Is the health of singletons born after frozen embryo transfer (FET) comparable to that of singletons born after fresh embryo transfer (ET) until early adulthood? SUMMARY ANSWER: The health of singletons born after FET does not differ from that of singletons born after fresh ET. WHAT IS KNOWN ALREADY: The differences in perinatal outcomes of children born after FET and fresh ET are well known. FET is associated with an increased risk of large-for-gestational-age but diminished risks of preterm birth (PTB), small-for-gestational-age and decreased perinatal mortality compared to fresh ET. However, knowledge on the long-term health after FET is scarce. STUDY DESIGN, SIZE, DURATION: This retrospective register-based cohort study compares singletons born after FET (n = 1825) between the years 1995 and 2006 to those born after fresh ET (n = 2933) and natural conception (NC, n = 31 136) with a mean follow-up time of 18-20 years. PARTICIPANTS/MATERIALS, SETTING, METHODS: Singletons born after FET were compared to those born after fresh ET and NC regarding the frequencies of diagnoses in the main ICD-10 chapters (International Statistical Classification of Diseases and Related Health Problems, 10th revision), the number of outpatient visits and hospital admissions, and mortality. Adjustments were made for PTB, maternal age, parity, socioeconomic status based on mother's occupation and offspring sex. The study combines data from the Finnish Medical Birth Register, the Finnish Care Register for Health Care (CRHC) and the Cause-of-Death Register at Statistics Finland. The Student's T-test was used for continuous variables, and the Chi-square test was used for categorical variables. Cox regression was used to estimate crude and adjusted hazard ratios (HRs and aHRs, respectively). A general linear model was used to compare the means of outpatient visits, hospital admissions and lengths of hospital stays per person. MAIN RESULTS AND THE ROLE OF CHANCE: No significant differences between the FET and fresh ET groups were found in the frequency of diagnoses in any of the ICD-10 chapters or in the parameters describing the need for hospital care. However, compared to the NC group, higher proportions in the FET group had outpatient visits in the hospital (93.5% vs 92.2%, aHR 1.23, 95% CI 1.17, 1.30) or hospital admissions (48% vs 46.5%, aHR 1.28, 95% CI 1.19, 1.37). Compared to the NC group, the FET group had elevated adjusted risks of diagnoses of infectious and parasitic diseases (aHR 1.24; 95% CI 1.11, 1.38), neoplasms (aHR 1.68; 95% CI 1.48, 1.91), diseases of the eye and adnexa, the ear or mastoid process (aHR 1.11; 95% CI 1.01, 1.21), the respiratory system (aHR 1.15; 95% CI 1.06, 1.23), the digestive system (aHR 1.17; 95% CI 1.05, 1.32), the skin or subcutaneous tissue (aHR 1.28; 95% CI 1.14, 1.43) and the genitourinary system (aHR 1.27; 95% CI 1.11, 1.45), as well as congenital malformations or chromosomal abnormalities (aHR 1.31; 95% CI 1.14, 1.50) and symptoms, signs or abnormal clinical or laboratory findings (aHR 1.25, 95% CI 1.16, 1.34). LIMITATIONS, REASONS FOR CAUTION: Only hospital-based inpatient and outpatient care is covered by the CRHC register, excluding milder cases diagnosed elsewhere. We were not able to study the effect of ART treatments and subfertility separately in our setting. In addition, although our cohort is reasonably sized, even larger cohorts would be needed to reliably study rare outcomes, such as cancer. WIDER IMPLICATIONS OF THE FINDINGS: For many ICD-10 chapters, we present the first published data on the long-term outcome of singletons born after FET. The results on FET versus fresh ET are reassuring, whereas the results on FET versus NC warrant further investigation. STUDY FUNDING/COMPETING INTEREST(S): Finnish government research funding was obtained for this study. Funding was also obtained from the Finnish Medical Society Duodecim, the Päivikki and Sakari Sohlberg Foundation, Orion Research Foundation, Finnish Society of Obstetrics and Gynaecology (research grants to A.M.T.) and Finnish government research funding. The funding sources were not involved in the planning or execution of the study. The authors have no competing interests to declare. TRIAL REGISTRATION NUMBER: N/A.

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.

Adolescent attachment to parents and peers in singletons and twins born with assisted and natural conception.

STUDY QUESTION: Does adolescent attachment to parents and peers differ between singletons and twins born with ART or natural conception (NC)? SUMMARY ANSWER: Adolescent attachment anxiety with the father was higher among NC singletons than among ART and NC twins, whereas attachment avoidance with the father was higher in ART singletons than in NC singletons and NC twins. No differences were found in attachment to the mother, best friend or romantic partner. WHAT IS KNOWN ALREADY: Most studies have not found differences between ART and NC singletons in parent-adolescent relationships, but twin relationships may be more at risk. No previous study has examined all four groups in the same study, or specifically looked at attachment relationships. STUDY DESIGN SIZE DURATION: This was an 18-year, prospective and controlled longitudinal study with families of 496 ART singletons, 101 ART twin pairs, 476 NC singletons and 22 NC twin pairs. Families were recruited during the second trimester of pregnancy; the ART group was recruited from five infertility clinics in Finland and the control group was recruited from a hospital outpatient clinic during a routine visit. PARTICIPANTS/MATERIALS SETTING METHODS: Mothers and fathers gave background information for this study during pregnancy, and during the child's first year and early school age (7-8 years). For the ART group, infertility characteristics and prenatal medical information was also obtained from the patient registry of the infertility clinics. Children (originally 50% girls) filled in electronic questionnaires related to their attachment to mother, father, best friend and romantic partner (Experiences in Close Relationships-Relationship Structures) at 17-19 years of age. MAIN RESULTS AND THE ROLE OF CHANCE: Adolescent attachment anxiety to father was higher in NC singletons than in ART twins, P = 0.004 and marginally higher than in NC twins, P = 0.06. Adolescent attachment avoidance to father was higher in ART singletons than in NC singletons, P = 0.006 and marginally higher than in NC twins, P = 0.055. LIMITATIONS REASONS FOR CAUTION: The sample size was small especially in the NC twin group and there was drop-out over the 18-year time period, especially among boys and families with lower parental education level. The study only included native Finnish-speaking families. The results could differ in a more diverse population. ART singletons were younger and had fewer siblings than ART twins and NC children, and ART and NC twins had more newborn health risks than ART and NC singletons. WIDER IMPLICATIONS OF THE FINDINGS: The study adds to a growing body of evidence that neither ART treatments nor being a twin places mother-child relationships or peer relationships at long-term risk. However, in our study, which was the first to examine both ART and twinhood simultaneously, we found that there may be more problems in father-adolescent relationships, but only in ART singletons and only related to attachment avoidance. Our findings suggest that men, as well as women, should receive enough support in pre- and peri-natal health care during and after infertility treatments. STUDY FUNDING/COMPETING INTERESTS: This study was funded by Academy of Finland (grant number 2501308988), the Juho Vainio Foundation and the Finnish Cultural Foundation. The authors report no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Probability of live birth after IVF/ICSI treatments in female early onset cancer survivors: a Finnish population-based registry study.

STUDY QUESTION: Does the probability of a live birth after fresh IVF/ICSI cycles with autologous oocytes differ in early onset female cancer survivors compared to their siblings? SUMMARY ANSWER: The probability of a live birth was similar in female cancer survivors and siblings after four fresh IVF/ICSI cycles. WHAT IS KNOWN ALREADY: Fertility preservation strategies are rapidly being developed to help female cancer patients who wish to have children later. However, there are only a few studies available on fertility treatments and following live births in female cancer survivors before fertility preservation strategies became available. In one of them, the probability of a live birth was reduced after assisted reproductive technology with autologous oocytes in cancer survivors compared to siblings. STUDY DESIGN, SIZE, DURATION: In this retrospective, register-based study, data from Finnish registers on cancer, birth and prescribed medications were merged to identify 8944 female cancer survivors (diagnosed with cancer between 1953 and 2012 at the age of 0-40 years) and 9848 female siblings of survivors eligible for IVF/ICSI treatments between January 1993 and December 2012. PARTICIPANTS/MATERIALS, SETTING, METHODS: Fresh IVF/ICSI cycles and following live birth rates (LBRs) within 22-48 weeks in cancer survivors and siblings at the age of 20-41 years were identified. A binomial regression model with log-link function was used to calculate risk ratio (RR) for live births after fresh IVF/ICSI cycles in survivors compared to siblings, adjusting for attained age and calendar time. A Poisson regression model was used to estimate incidence rate ratios (IRRs) for an IVF/ICSI treatment, as well as overall live births, including both pregnancies after fertility treatments and spontaneous pregnancies, in survivors compared to siblings. MAIN RESULTS AND THE ROLE OF CHANCE: We observed an overall decreased LBR, irrespective of IVF/ICSI treatments, in cancer survivors compared to siblings (IRR 0.68, 95% CI 0.64-0.71). All in all, 179 (2.0%) survivors and 230 (2.3%) siblings were prescribed fertility drugs for IVF/ICSI treatments (IRR 0.72, 95% CI 0.62-0.84). For the first fresh IVF/ICSI cycle, the LBR was 17.2% among survivors and 15.7% among siblings (RR 1.13, 95% CI 0.72-1.87). The mean LBR after four fresh IVF/ICSI cycles was not statistically different in survivors compared to siblings. LIMITATIONS, REASONS FOR CAUTION: In this study, only IVF/ICSI treatments with autologous oocytes were included. The probability of a live birth after a frozen embryo transfer or oocyte donation could not be evaluated in this study. Information on miscarriages, extrauterine pregnancies or termination of pregnancies was not available. WIDER IMPLICATIONS OF THE FINDINGS: For those early onset cancer survivors, who received IVF/ICSI treatments, the probability of live birth was not different from siblings who received IVF/ICSI treatments. However, an overall decreased LBR, irrespective of IVF/ICSI treatments, was observed in cancer survivors compared to siblings, indicating that cancer survivors receiving IVF/ICSI treatments in our study consisted of a selected group with at least a moderate ovarian reserve. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by a grant from the Cancer Foundation (Finland) (grant number 130079) and by a grant from LähiTapiola. The authors have no potential conflicts 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.

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.

Low anti-Müllerian hormone level is not a risk factor for early pregnancy loss in IVF/ICSI treatment.

STUDY QUESTION: Is a low (<1.0 µg/L) or moderately low (1.0-1.9 µg/L) serum anti-Müllerian hormone (AMH) level a risk factor for early pregnancy loss in IVF/ICSI with a fresh or frozen-thawed embryo transfer (ET)? SUMMARY ANSWER: A low or moderately low serum AMH level does not associate with miscarriage, non-visualized pregnancy loss or overall early pregnancy loss rate in the IVF/ICSI treatment. WHAT IS KNOWN ALREADY: Low AMH predicts poor ovarian response and small oocyte yield in IVF/ICSI treatment, but its value in the evaluation of live birth rate (LBR) is modest. Little is known about the risk of early pregnancy loss in ART among women with low AMH. STUDY DESIGN, SIZE, DURATION: A retrospective cohort study on 1383 women undergoing their first oocyte retrieval for IVF/ICSI in Helsinki University Hospital in Helsinki, Finland, between 2012 and 2016, with all associated fresh (n = 1315) and frozen-thawed (n = 1418) ET cycles finished by August 2018. AMH was measured within 12 months before the IVF/ICSI stimulation. PARTICIPANTS/MATERIALS, SETTING, METHODS: Of all the women, 235 (17.0%) had low (<1.0 µg/L), 278 (20.1%) had moderately low (1.0-1.9 µg/L) and 870 (62.9%) had normal (≥2.0 µg/L) AMH. The primary outcomes were miscarriage, non-visualized pregnancy loss and early pregnancy loss (miscarriage and non-visualized pregnancy loss combined) after fresh or frozen-thawed ET. The impact of AMH on these outcomes was calculated in three populations: among all women who became pregnant, among women with AMH ≤6.0 µg/L and in a population weighted by the inverse probability of becoming pregnant (inverse probability weighting, IPW). The impact of AMH was also assessed on the secondary outcomes, cumulative pregnancy rate (cPR) and cumulative live birth rate (cLBR) across all ET cycles in the woman's first IVF/ICSI. Potential confounders (the woman's age, overweight, smoking, history of endometriosis and underlying medical conditions) adjusted the final results. MAIN RESULTS AND THE ROLE OF CHANCE: Of 1123 pregnancies, 285 (25.4%) ended in non-visualized pregnancy loss and 143 (12.7%) in miscarriage. The LBR was 24.6% per ET (673/2733). Low or moderately low AMH, compared with normal AMH, did not associate with miscarriage or non-visualized pregnancy loss in analyses among all women who became pregnant (adjusted relative risk (RR) for miscarriage vs live birth, 0.70 and 95% CI 0.42-1.17 in low AMH and adjusted RR, 1.00 and 95% CI, 0.68-1.49 in moderately low AMH; adjusted RR for non-visualized pregnancy loss vs live birth, 0.90 and 95% CI, 0.65-1.23 in low AMH and adjusted RR, 1.09 and 95% CI 0.85-1.41 in moderately low AMH), nor did low or moderately low AMH associate with the overall early pregnancy loss rate (adjusted RR for early pregnancy loss vs live birth, 0.86 and 95% CI, 0.68-1.10 in low AMH and adjusted RR, 1.01 and 95% CI, 0.86-1.27 in moderately low AMH). Results remained similar after restricting the analysis to women with AMH ≤6.0 µg/L. Women with low or moderately low AMH had fewer pregnancies and live births than women with normal AMH in their first IVF/ICSI (cPR/cLBR in women with low AMH 50.6/34.0%, moderately low AMH 59.0/36.3% and normal AMH 68.3/49.2%). When the lower probability for pregnancy was considered by using IPW, women with low or moderately low AMH did not have a higher risk for miscarriage, non-visualized pregnancy loss or overall early pregnancy loss compared with women with normal AMH. LIMITATIONS, REASONS FOR CAUTION: The number of miscarriages in women with low AMH was moderately small, limiting the power of the study. The real-world clinical setting of the study restricted the ability to control for all factors causing selection bias. WIDER IMPLICATIONS OF THE FINDINGS: The cLBR was higher among women with normal AMH than among women with low or moderately low AMH in their first IVF/ICSI treatment because these women had more oocytes and embryos. Women with low or moderately low AMH did not have an increased risk for early pregnancy loss. This information is reassuring for couples and useful in counseling. These results are also valuable when assessing the overall effectiveness of IVF/ICSI treatment. STUDY FUNDING/COMPETING INTEREST(S): Research funds from Helsinki University Hospital (no. TYH2018232), Hyvinkää Hospital (no. M3080TUT18) and the Emil Aaltonen Foundation for P.P. Grants from the Paulo Foundation and the Finnish Medical Foundation for H.H. The authors report no conflicts of interest. TRIAL REGISTRATION NUMBER: HUS/138/2017.

The risk of psychiatric disorders among Finnish ART and spontaneously conceived children: Finnish population-based register study.

Evidence regarding the psychiatric morbidity of children born after Assisted Reproductive Techniques (ART) is inconsistent and limited. While normal mental well-being for ART children is usually reported, concerns are still being raised. Previous studies examine only some psychiatric disorders, but not all of them, ignore the impact of multiplicity, and limit the follow-up time to childhood. We examined all psychiatric diagnoses for singletons until their young adulthood. The aim was to study whether the risk of psychiatric disorders differs between ART and spontaneously conceived (SC) singletons until young adulthood. This retrospective Finnish population-based register study includes all ART and SC live-born children born in Finland during 1990-2013 and their hospital care in 1990-2014 (n = 1,425,975 of which 1,385,956, 97.2% were singletons). After excluding multiples, the final population included 17,610 ART and 1,368,346 SC singletons in 1990-2013 from the Finnish Medical Birth Registry. These data were linked to the Finnish Hospital Discharge Registry with the child's and mother's encrypted IDs. ART singletons had fewer psychiatric diagnoses (ART 10.2%, n = 1796, SC 12.0%, n = 164,408), but they received their diagnoses earlier (mean 8.3 years old, SD 5.0) than SC singletons (mean 10.5 years old, SD 5.7). After adjusting for confounding factors, ART singletons had an increased likelihood of getting a psychiatric diagnosis until young adulthood and the results were similar for boys (adjusted hazard ratios [aHR] = 1.16, 95% confidence interval (CI) 1.10-1.24) and girls (aHR = 1.25, 95% CI 1.16-1.35). We conclude that ART children receive their psychiatric diagnoses earlier than SC children, in particular during childhood and early adolescence. After adjusting for confounding factors ART children a slightly increased likelihood of any psychiatric diagnosis compared to SC controls.

Mortality of midlife women with surgically verified endometriosis-a cohort study including 2.5 million person-years of observation.

STUDY QUESTION: Is all-cause and cause-specific mortality increased among women with surgically verified endometriosis? SUMMARY ANSWER: The all-cause and cause-specific mortality in midlife was lower throughout the follow-up among women with surgically verified endometriosis compared to the reference cohort. WHAT IS KNOWN ALREADY: Endometriosis has been associated with an increased risk of comorbidities such as certain cancers and cardiovascular diseases. These diseases are also common causes of death; however, little is known about the mortality of women with endometriosis. STUDY DESIGN, SIZE, DURATION: A nationwide retrospective cohort study of women with surgically verified diagnosis of endometriosis was compared to the reference cohort in Finland (1987-2012). Follow-up ended at death or 31 December 2014. During the median follow-up of 17 years, 2.5 million person-years accumulated. PARTICIPANTS/MATERIALS, SETTING, METHODS: Forty-nine thousand nine hundred and fifty-six women with at least one record of surgically verified diagnosis of endometriosis in the Finnish Hospital Discharge Register between 1987 and 2012 were compared to a reference cohort of 98 824 age- and municipality-matched women. The age (mean ± standard deviation) of the endometriosis cohort was 36.4 ± 9.0 and 53.6 ± 12.1 years at the beginning and at the end of the follow-up, respectively. By using the Poisson regression models the crude and adjusted all-cause and cause-specific mortality rate ratios (MRR) and 95% confidence intervals (CI) were assessed. Calendar time, age, time since the start of follow-up, educational level, and parity adjusted were considered in the multivariate analyses. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 1656 and 4291 deaths occurred in the endometriosis and reference cohorts, respectively. A lower all-cause mortality was observed for the endometriosis cohort (adjusted MRR, 0.73 [95% CI 0.69 to 0.77])-there were four deaths less per 1000 women over 10 years. A lower cause-specific mortality contributed to this: the adjusted MRR was 0.88 (95% CI 0.81 to 0.96) for any cancer and 0.55 (95% CI 0.47 to 0.65) for cardiovascular diseases, including 0.52 (95% CI 0.42 to 0.64) for ischemic heart disease and 0.60 (95% CI 0.47 to 0.76) for cerebrovascular disease. Mortality due to alcohol, accidents and violence, respiratory, and digestive disease-related causes was also decreased. LIMITATIONS, REASONS FOR CAUSATION: These results are limited to women with endometriosis diagnosed by surgery. In addition, the study does not extend into the oldest age groups. The results might be explained by the characteristics and factors related to women's lifestyle, and/or increased medical attention and care received, rather than the disease itself. WIDER IMPLICATIONS OF THE FINDINGS: These reassuring data are valuable to women with endometriosis and to their health care providers. Nonetheless, more studies are needed to address the causality. STUDY FUNDING/COMPETING INTEREST: This research was funded by the Hospital District of Helsinki and Uusimaa and The Finnish Medical Foundation. None of the authors report any competing interest in relation to the present work; all the authors have completed the disclosure form.

Serum antibody response to Chlamydia trachomatis TroA and HtrA in women with tubal factor infertility.

Persistent genital chlamydial infection may lead to tubal factor infertility (TFI). Chlamydia trachomatis TroA and HtrA are proteins expressed during persistent chlamydial infection in vitro. We studied serum IgG antibody response against these proteins by EIA in women with TFI and in subfertile women without tubal pathology. Altogether, 22 of 258 subfertile women (8.5%) had TFI which was unilateral in 17 cases and bilateral in 5 cases. Overall, 55 (21.3%) of the 258 women had TroA and 39 (15.1%) had HtrA antibodies. Seropositivity to TroA and HtrA was more common among women with TFI than women with other causes for subfertility (45.5 vs. 19.1%, p = 0.004 for TroA; 36.4 vs. 13.1%, p = 0.004 for HtrA). Mean absorbance values and the prevalence of TroA and HtrA antibodies increased with increasing severity of TFI. On the basis of our results, TroA and HtrA serology has the potential to be further developed to a specific biomarker for C. trachomatis-related TFI.

Cardiorespiratory fitness and health-related quality of life in women at risk for gestational diabetes.

This study examined the associations of cardiorespiratory fitness (CRF) and leisure-time physical activity (LTPA) with health-related quality of life (HRQoL) in women at risk for gestational diabetes mellitus (GDM). The participants were 39 women planning pregnancy with a history of GDM and/or BMI >29 kg/m2 . We assessed CRF by measuring maximal oxygen consumption (VO2max ) during incremental cycle ergometer exercise until voluntary fatigue. LTPA was self-reported, and HRQoL assessed with the SF-36 Health Survey (SF-36). The mean (SD) VO2max was 27 (6) mL·kg-1 ·min-1 , and the mean LTPA was 2.6 (1.7) h/wk. After controlling for BMI, VO2max was positively associated with the SF-36 General Health scale (ß 1.27, 95% CI: 0.09, 2.44, P=.035) and the Physical Component Summary (ß 0.48, 95% CI: 0.14, 0.82, P=.007). The General Health scale (P=.023) and the Physical Component Summary (P=.011) differed even between those with very poor and poor CRF. After controlling for BMI, LTPA was positively associated with the SF-36 Physical Functioning scale (rs =.34, P=.039), the General Health scale (ß 3.74, 95% CI: 0.64, 6.84, P=.020), and the Physical Component Summary (ß 1.13 95% CI: 0.19, 2.06, P=.020). To conclude, CRF and LTPA were positively associated with perceived general health and physical well-being in women planning pregnancy and at risk for GDM. Even a slightly better CRF would be beneficial for well-being among women with low levels of CRF.

The effect of dietary counselling on food intakes in pregnant women at risk for gestational diabetes: a secondary analysis of a randomised controlled trial RADIEL.

BACKGROUND/OBJECTIVES: The prevalence of gestational diabetes mellitus (GDM) is increasing worldwide. GDM may be prevented by improving the diets of pregnant women. The objective of this study was to evaluate the effect of dietary counselling on the diets of pregnant women at GDM risk. SUBJECTS/METHODS: This study was a secondary analysis of a randomised controlled trial the Finnish gestational diabetes prevention study (RADIEL) in which pre-pregnant and pregnant women with previous GDM or BMI ⩾30 kg/m(2) were allocated into two groups, namely the control and the intervention groups. The control group received standard antenatal dietary counselling according to the Finnish Nutrition Recommendations. The intervention group participated in one individual dietary counselling session and one group dietary counselling session in addition to the standard counselling. This study included women who were recruited during pregnancy. To assess changes in food intake, food-intake questionnaires were collected during the first and the second trimester of pregnancy. Bootstrap type analysis of covariance was used, and 242 participants were included in the final analysis to study changes in food intake. RESULTS: The intakes of low-fat cheese (baseline adjusted mean 0.09 times/day; 95% confidence interval (CI) 0.07, 0.24; P=0.040) and fish (baseline adjusted mean 0.28 times per week; 95% CI 0.08, 0.49; P=0.011) showed a significant increase in the intervention group compared with the control group. CONCLUSIONS: This study showed that dietary counselling in early pregnancy can lead to modest dietary improvements in pregnant women at GDM risk.

Physical health of singleton children born after frozen embryo transfer using slow freezing: a 3-year follow-up study.

STUDY QUESTION: Are there differences in the physical health of singleton children born after frozen embryo transfer (FET) compared with children born after fresh embryo transfer (fresh ET)? SUMMARY ANSWER: Register-based health indicators were similar among FET and fresh ET singletons during a 3-year follow-up. WHAT IS KNOWN ALREADY: Large cohort studies have shown that perinatal outcomes are similar or even better in FET than fresh ET children. The early childhood morbidity among FET and fresh ET children has been shown to be quite similar, but so far these studies have been small. The short-term health outcomes of assisted reproductive technology (ART) children have been shown to be slightly worse compared with spontaneously conceived children. STUDY DESIGN, SIZE, DURATION: This register-based study includes women who had undergone ART treatments leading to singleton live births (n = 4758 children) in 1995-2006. A 10% random sample of women with spontaneous pregnancies from the Finnish Medical Birth Register (FMBR) served as the reference group (n = 31 137 children). The children were identified through the FMBR by using the mother's personal identification (ID) number. Children's ID numbers were linked with two nationwide registries; the Finnish Hospital Discharge Register and the Cause-of-Death Register at Statistics Finland. Information on all visits was received until 2009 using ICD-10 codes. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study includes 1825 children born after FET, 2933 children born after fresh ET and 31 137 children born after spontaneous pregnancies. The risk estimates for diseases were adjusted for the child's year of birth and maternal age, parity, socio-economic status and prematurity. The study focused on the differences between FET and fresh ET children. MAIN RESULTS AND THE ROLE OF CHANCE: Most health indicators were similar among FET and fresh ET children during the 3-year follow-up. The most common discharge diagnoses, including gastroenteritis and colitis, otitis, upper and lower respiratory diseases, asthma and allergies were similar between the ART groups. A large proportion of FET children (70.1%) and fresh ET children (69.9%) had visited a hospital at least once (P = 0.877). The risk of hospital admission did not differ between the two groups after adjusting for premature births [adjusted odds ratio (aOR) 1.01; 0.88-1.17]. Comparing with children born after spontaneously conceived pregnancies, the risk of hospital admission was slightly increased in the ART group, even after adjusting for premature births (aOR 1.10; 1.02-1.19). LIMITATIONS, REASONS FOR CAUTION: Due to the study design, we were not able to control for some parental background factors, such as the cause and length of infertility. Furthermore, the health registries do not include data on the growth of the children. Our findings are generalizable only to the slow-freezing method. WIDER IMPLICATIONS OF THE FINDINGS: Our study provides further evidence of the safety of embryo cryopreservation. The early physical health of FET children is similar to that of children born after fresh ET. STUDY FUNDING/COMPETING INTERESTS: This study was funded by the University Hospital of Oulu and Helsinki, Finland. The National Institute for Health and Welfare (THL) covered the data linkages and the work of Mika Gissler. There are no competing interests to be reported.

Risk of hypertensive disorders in pregnancies following assisted reproductive technology: a cohort study from the CoNARTaS group.

STUDY QUESTION: Is the risk of hypertensive disorders in pregnancies conceived following specific assisted reproductive technology (ART) procedures different from the risk in spontaneously conceived (SC) pregnancies? SUMMARY ANSWER: ART pregnancies had a higher risk of hypertensive disorders, in particular following cryopreservation, with the highest risk seen in twin pregnancies following frozen-thawed cycles. WHAT IS KNOWN ALREADY: The risk of hypertensive disorders is higher in ART pregnancies than in SC pregnancies. The increased risk may be partly explained by multiple pregnancies and underlying infertility, but a contribution from specific ART procedures has not been excluded. STUDY DESIGN, SIZE, DURATION: Population-based cohort study, including sibling design with nationwide data from health registers in Sweden, Denmark and Norway. PARTICIPANTS/MATERIALS, SETTING, METHODS: All registered ART pregnancies and a sample of SC pregnancies with gestational age ≥22 weeks from 1988 to 2007 were included. ART singleton pregnancies (n = 47 088) were compared with SC singleton pregnancies (n = 268 599), matched on parity and birth year. ART twin pregnancies (n = 10 918) were compared with SC twin pregnancies (46 674). We used logistic regression to estimate adjusted odds ratios and risk differences for hypertensive disorders in pregnancies following IVF, ICSI and fresh or frozen-thawed cycles. We also compared fresh and frozen-thawed cycles within mothers who had conceived following both procedures using conditional logistic regression (sibling analysis). MAIN RESULTS AND THE ROLE OF CHANCE: Hypertensive disorders were reported in 5.9% of ART singleton and 12.6% of ART twin pregnancies. Comparing singleton pregnancies, the risk of hypertensive disorders was higher after all ART procedures. The highest risk in singleton pregnancies was seen after frozen-thawed cycles [risk 7.0%, risk difference 1.8%, 95% confidence interval (CI) 1.2-2.8]. Comparing twin pregnancies, the risk was higher after frozen-thawed cycles (risk 19.6%, risk difference 5.1%, 95% CI 3.0-7.1), but not after fresh cycles. In siblings, the risk was higher after frozen-thawed cycles compared with fresh cycles within the same mother (odds ratio 2.63, 95% CI 1.73-3.99). There were no clear differences in risk for IVF and ICSI. LIMITATIONS, REASONS FOR CAUTION: The number of ART siblings in the study was limited. Residual confounding cannot be excluded. In addition, we did not have information on all SC pregnancies in each woman's history, and could therefore not compare risk in ART versus SC pregnancies in the same mother. WIDER IMPLICATIONS OF THE FINDINGS: Pregnancies following frozen-thawed cycles have a higher risk of hypertensive disorders, also when compared with fresh cycle pregnancies by the same mother. The safety aspects in frozen-thawed cycles merit further attention. STUDY FUNDING/COMPETING INTERESTS: Funding was received from the European Society for Human Reproduction and Embryology, the University of Copenhagen, the Danish Agency for Science, Technology and Innovation, the Nordic Federation of Societies of Obstetrics and Gynecology and the Liaison Committee between the Central Norway Regional Health Authority and the Norwegian University of Science and Technology. None of the authors has any competing interests to declare.

Contribution of IL-12A and IL-12B polymorphisms to Chlamydia trachomatis-specific cell-mediated immune responses.

Inherited variance in the IL-12B gene is associated with susceptibility to Chlamydia trachomatis-induced tubal factor infertility and disease severity. In this study, our aim was to discover how polymorphisms in IL-12-coding genes influence C. trachomatis-induced immune responses and IL-12 production. The study population consisted of 240 women. IL-12A and IL-12B single nucleotide polymorphisms (SNPs) were determined from isolated DNA using the Sequenom system with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. We studied lymphocyte proliferative (LP) responses to C. trachomatis strains E and F elementary bodies (EBs) and recombinant chlamydial heat-shock protein 60 (CHSP60) antigen. IL-12p40 and IL-12p70 levels were measured using the BD Flex Set method. We found a statistically significant association between the C. trachomatis EB antigen-specific LP response and the rs2853694 SNP (P = 0.02). Our study demonstrates that the IL-12 cytokine family is involved in C. trachomatis-specific immune responses. Moreover, C. trachomatis-induced IL-12 production and the IL-12B rs2853694 SNP partially explain individual variation in the C. trachomatis LP response.

Trends in perinatal health after assisted reproduction: a Nordic study from the CoNARTaS group.

STUDY QUESTIONS: Has the perinatal outcome of children conceived after assisted reproductive technology (ART) improved over time? SUMMARY ANSWER: The perinatal outcomes in children born after ART have improved over the last 20 years, mainly due to the reduction of multiple births. WHAT IS KNOWN AND WHAT THIS PAPER ADDS: A Swedish study has shown a reduction in unwanted outcomes over time in children conceived after ART. Our analyses based on data from more than 92 000 ART children born in four Nordic countries confirm these findings. STUDY DESIGN: Nordic population-based matched cohort study with ART outcome and health data from Denmark, Finland, Norway and Sweden. PARTICIPANTS, SETTING AND METHODS: We analysed the perinatal outcome of 62 379 ART singletons and 29 758 ART twins, born from 1988 to 2007 in four Nordic countries. The ART singletons were compared with a control group of 362 215 spontaneously conceived singletons. Twins conceived after ART were compared with all spontaneously conceived twins (n = 122 763) born in the Nordic countries during the study period. The rates of several adverse perinatal outcomes were stratified into the time periods: 1988-1992; 1993-1997; 1998-2002 and 2003-2007 and presented according to multiplicity. MAIN RESULTS AND ROLE OF CHANCE: For singletons conceived after ART, a remarkable decline in the risk of being born preterm and very preterm was observed. The proportion of ART singletons born with a low and very low birthweight also decreased. Finally, the stillbirth and infant death rates have declined among both ART singletons and twins. Throughout the 20 year period, fewer ART twins were stillborn or died during the first year of life compared with spontaneously conceived twins, presumably due to the lower proportion of monozygotic twins among the ART twins. LIMITATIONS, REASONS FOR CAUTION: We were not able to adjust for some potential confounders such as BMI, smoking, length or cause of infertility. The Nordic ART populations have changed over time, and in recent years, both less as well as severely reproductive ill couples are being treated. This may have affected the observed trends. WIDER IMPLICATIONS OF THE FINDINGS: It is assuring that data from four countries confirm an overall improvement over time in the perinatal outcomes of children conceived after ART. Furthermore, data show the beneficial effect of single embryo transfer, not only in regard to lowering the rate of multiples but also concerning the health of singletons. STUDY FUNDING/COMPETING INTERESTS: The European Society for Human Reproduction and Embryology (ESHRE), the University of Copenhagen and the Danish Agency for Science, Technology and Innovation has supported the project. The CoNARTaS group has received travel and meeting funding from the Nordic Federation of Obstetrics and Gynecology (NFOG). None of the authors has any competing interests to declare.

Major congenital anomalies in children born after frozen embryo transfer: a cohort study 1995-2006.

STUDY QUESTION: Is there a different risk for major congenital anomalies (CAs) in children born after frozen-thawed embryo transfer (FET) compared with children born after fresh embryo transfer (ET)? SUMMARY ANSWER: Children born after FET have a similar risk of developing major CAs as children born after fresh ET. WHAT IS KNOWN ALREADY: The perinatal outcome in children born after FET is as good as that after fresh ET. Children born as a result of assisted reproductive technology (ART) have an increased risk for CAs when compared with spontaneously conceived children, but the knowledge on the risk for CAs in specific organ systems of children born after FET is limited. STUDY DESIGN, SIZE, DURATION: This register-based cohort study includes women who have undergone ART treatments with ET leading to singleton births (n = 4772) between the years 1995 and 2006. The women were identified from the registers of the infertility clinics, and the corresponding births were matched with data from the Finnish Medical Birth Register (FMBR). The 10% random sample of women with spontaneous pregnancies from the FMBR served as the reference group (n = 31,243). The study data were linked with the Register of Congenital Malformations using the mothers' and children's personal identification numbers to get information on CAs. Furthermore, the personal identification numbers of the ART women were linked with the Register of Induced Abortions to find their selective terminations of pregnancy for severe foetal anomalies. PARTICIPANTS, SETTING, METHODS: The study was focused on singleton births and included 1830 children born after FET, 2942 children born after fresh ET and 31 243 children born after spontaneous pregnancies. Only major CAs were analysed in keeping with European Concerted Action on Congenital Anomalies and Twins. The risk estimates for CAs were adjusted for the children's year of birth and maternal age, parity and socioeconomic status. The total prevalence of major CAs was counted, including both births and selective terminations of pregnancy for major fetal anomalies (n = 33). MAIN RESULTS AND THE ROLE OF CHANCE: Among singletons at least one major CA was reported in 77 cases (4.2%) in the FET group, 132 cases (4.5%) in the fresh ET group and 994 cases (3.2%) in the reference group. The risk for at least one major CA of the children born after FET was not increased compared with the children born after fresh ET [adjusted odd ratio (aOR) 0.95; 0.71-1.27]. Furthermore, no increased risks according to the organ system affected were found between these two ART groups. When comparing the children born after ART (FET and fresh ET) with the reference group children, the risk of having at least one major CA was moderately increased in the ART group (aOR 1.24; 1.05-1.47). LIMITATIONS, REASONS FOR CAUTION: Because of the study design we were neither able to examine the aetiology of infertility nor could we compare the data with a group of subfertile women to account for the effect of infertility per se on CAs. WIDER IMPLICATIONS OF THE FINDINGS: Perinatal outcomes of FET children, including the risks for CAs, are good and comparable with outcomes of other ART children indicating that slow freezing is a safe method to use during ART treatments. STUDY FUNDING/COMPETING INTEREST(S): University Hospital of Oulu and Helsinki, Finland. THL covered the data linkages and the work of Annukka Ritvanen and Mika Gissler. There are no competing interests to be reported.