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.

First live birth before surgical verification of endometriosis-a nationwide register study of 18 324 women.

STUDY QUESTION: Do women with endometriosis have lower first live birth rate before surgical diagnosis than women without verified endometriosis? SUMMARY ANSWER: Compared to reference women, the incidence of first live birth was lower in women prior to surgical verification of endometriosis irrespective of the type of endometriosis. WHAT IS KNOWN ALREADY: Endometriosis is associated with pain and reduced fertility. The mechanism of infertility is partly explained by anatomical, endocrinological, and immunological changes. Over the past decades, the treatment of both endometriosis and infertility has evolved. Knowledge of fertility far before surgical diagnosis of endometriosis in large cohorts and of different types of endometriosis has been lacking. The diagnostic delay of endometriosis is long, 6-7 years. STUDY DESIGN, SIZE, DURATION: Retrospective population-based cohort study focused on the time period before the surgical verification of endometriosis. All women with surgical verification of endometriosis in 1998-2012 were identified from the Finnish Hospital Discharge Register and the reference cohort from the Central Population Register. Data on deliveries, gynecological care, and sociodemographic factors before the surgical diagnosis were gathered from Finnish national registers maintained by the Finnish Institute for Health and Welfare, the Digital and Population Data Services Agency, and Statistics Finland. PARTICIPANTS/MATERIALS, SETTING, METHODS: All women aged 15-49 years at the time of surgical verification of endometriosis (ICD-10: N80.1-N80.9) in Finland during 1998-2012 were identified (n = 21 620). Of them, we excluded women born in 1980-1999 due to the proximity of the surgical diagnosis (n = 3286) and women left without reference (n = 10) for the final endometriosis cohort of 18 324 women. From the final cohort, we selected sub-cohorts of women with isolated diagnosis of ovarian (n = 6384), peritoneal (n = 5789), and deep (n = 1267) endometriosis. Reference women were matched by age and residence and lacked registered clinical or surgical diagnosis of endometriosis (n = 35 793). The follow-up started at the age of 15 years and ended at the first birth, sterilization, bilateral oophorectomy, hysterectomy, or until the surgical diagnosis of endometriosis or corresponding index day-whichever came first. Incidence rate (IR) and the incidence rate ratio (IRR) of first live birth before the surgical verification of endometriosis with corresponding CIs were calculated. In addition, we reported the fertility rate of parous women (the number of all children divided by the number of parous women in the cohort) until the surgical verification of endometriosis. The trends in first births were analysed according to the women's birth cohort, type of endometriosis, and age. MAIN RESULTS AND THE ROLE OF CHANCE: Surgical diagnosis of endometriosis was set at the median age of 35.0 years (IQR 30.0-41.4). Altogether 7363 women (40.2%) with endometriosis and 23 718 (66.3%) women without endometriosis delivered a live born infant before the index day (surgery). The IRs of the first live birth per 100 person-years were 2.64 (95% CI 2.58-2.70) in the endometriosis cohort and 5.21 (95% CI 5.15-5.28) in the reference cohort. Between the endometriosis sub-cohorts, the IRs were similar. The IRR of the first live birth was 0.51 (95% CI 0.49-0.52) between the endometriosis and reference cohorts. Fertility rate per parous woman before the surgical diagnosis was 1.93 (SD 1.00) and 2.16 (SD 1.15) in the endometriosis and reference cohorts (P < 0.01). The median age at the first live birth was 25.5 (IQR 22.3-28.9) and 25.5 (IQR 22.3-28.6) years (P = 0.01), respectively. Between the endometriosis sub-cohorts, women in the ovarian sub-cohort were the oldest at the time of surgical diagnosis with the median age of 37.2 years (IQR 31.4-43.3), (P < 0.001). Altogether 44.1% (2814) of the women with ovarian, 39.4% (2282) with peritoneal, and 40.8% (517) with deep endometriosis delivered a live born infant before the diagnosis. IRRs between the endometriosis sub-cohorts did not differ. Fertility rate per parous woman was lowest, 1.88 (SD 0.95), in the ovarian sub-cohort compared to 1.98 (SD 1.07) in the peritoneal and 2.04 (SD 0.96) in deep endometriosis (P < 0.001). Women with ovarian endometriosis were oldest at first live birth compared to women in other sub-cohorts with a median age of 25.8 years (IQR 22.6-29.1) (P < 0.001). Cumulative distributions of first live birth were presented according to age at first live birth and birth cohorts of the participants. LIMITATIONS, REASONS FOR CAUTION: The increasing age at first live birth, increasing practice of clinical diagnostics, conservative treatment of endometriosis, a possible effect of coexisting adenomyosis, and use of artificial reproductive treatments should be considered when assessing the results. In addition, the study is limited due to possible confounding effects of socioeconomic factors, such as level of education. It should be noted that, in this study, we assessed parity only during the years preceding the surgical verification of endometriosis. WIDER IMPLICATIONS OF THE FINDINGS: The need for early diagnosis and relevant treatment of endometriosis appears clear given the impairment of fertility prior to its surgical verification. STUDY FUNDING/COMPETING INTEREST(S): The study was funded by the Hospital District of Helsinki and Uusimaa and by Finska Läkaresällskapet. The authors report no conflicts of interest. All authors have completed the ICMJE Disclosure form. TRIAL REGISTRATION NUMBER: N/A.

Postmenopausal hormone therapy in prior pre-eclamptic women: a nationwide cohort study in Finland.

OBJECTIVE: We compared the trends of hormone therapy (HT) use among women with and without a history of pre-eclampsia. METHODS: This national cohort study consisted of women with a pre-eclamptic pregnancy (n = 31,688) or a normotensive pregnancy (n = 91,726) (controls) during 1969-1993. The data on their use of HT during 1994-2019 were traced from the National Medicine Reimbursement Register. RESULTS: Both women with a history of pre-eclampsia and controls initiated HT at a mean age of 49.9 years. Cumulative HT™ use during the total follow-up did not differ between the groups (31.1% vs. 30.6%, p = 0.066). However, HT use in previously pre-eclamptic women was less common in 1994-2006 (20.2% vs. 22.4%, p < 0.001) and more common in 2007-2019 (22.1% vs. 21.1%, p < 0.001) than in controls. This trend was also seen in the annual changes of HT starters. Women with a history of pre-eclampsia used HT for a shorter time (6.3 vs. 7.1 years, p < 0.001). CONCLUSIONS: In contrast to controls, HT use in previously pre-eclamptic women increased during the last half of the follow-up. This may reflect the changes in the international recommendations, the increased awareness of pre-eclampsia-related cardiovascular risk later in life and the aim to diminish this risk with HT.

Association of genetic disorders and congenital malformations with premature ovarian insufficiency: a nationwide register-based study.

STUDY QUESTION: Are genetic disorders and congenital malformations associated with premature ovarian insufficiency (POI)? SUMMARY ANSWER: A wide range of genetic disorder and congenital malformation diagnoses are associated with POI, especially early onset POI. WHAT IS KNOWN ALREADY: POI is known to be associated with some genetic disorders, such as Turner syndrome and Fragile X premutation. Multiple genetic syndromes, such as ataxia teleangiectasia and galactosemia, have also been associated with an increased risk of POI, and many of these genetic syndromes manifest with various congenital malformations. In previous studies, a genetic aetiology has been found for 7-15% of POI cases. STUDY DESIGN, SIZE, DURATION: This population-based study included 5011 women diagnosed with POI in 1988-2017. The data were collected from various national registries and covers women with POI nationwide. PARTICIPANTS/MATERIALS, SETTING, METHODS: We identified 5011 women diagnosed with POI from 1988 to 2017 from the drug reimbursement registry of the Social Insurance Institution of Finland. Women with surgical POI (bilateral oophorectomy for benign indications) were not included. We selected four population controls per woman with POI matched by month and year of birth and municipality of residence. Diagnostic codes for genetic disorders and congenital malformations (GD/CM) for the cases and controls were searched from the Hospital Discharge Register. Binary logistic regression was used to compare the odds for GD/CM among cases and controls. To minimize bias, for the statistical analyses, we excluded diagnoses which were reported <2 years prior to the index date. MAIN RESULTS AND THE ROLE OF CHANCE: Of the women with POI, 15.9% (n = 797) had at least one diagnostic code for GD or CM. The odds ratio (OR) for Turner syndrome was 275 (95% CI 68.1-1110), and for other sex chromosome abnormalities, it was 12.7 (95% CI 4.1-39.1). For autosomal single gene disorders, the OR was 16.5 (95% CI 6.2-43.7). Women with POI had a higher odds of having a GD/CM diagnosis in all categories. The OR for GD/CM diagnoses was highest among the youngest POI patients (10-14 years old, OR 24.1, 95% CI 15.1-38.2). The odds of having POI were higher the more GD or CM diagnoses a woman had. LIMITATIONS, REASONS FOR CAUTION: Some women with POI might not have sought help for their symptoms and therefore remain undiagnosed. Due to the register-based nature of our study, we did not have access to more specific genetic diagnoses than international classification of diseases offers. WIDER IMPLICATIONS OF THE FINDINGS: GD/CM diagnoses were strongly associated with POI, especially when POI was diagnosed at a young age. The risk of POI was highest in women with multiple GD/CM diagnoses. Early onset POI can be a sign of underlying genetic disorder or congenital anomaly, and this should serve as a reminder for clinicians to consider further examinations. To avoid unnecessary delay in the diagnosis of POI and starting relevant hormone replacement therapy treatment, clinicians should be aware of these associations. STUDY FUNDING/COMPETING INTEREST(S): Oulu University Hospital financially supported this work. H.S. has received personal grants from the Finnish Menopause Society, Oulu Medical Research Foundation, and Finnish Research Foundation of Gynaecology and Obstetrics. S.S. has received grants from the Finnish Menopause Society, the Finnish Medical Foundation, and the Juho Vainio Foundation. None of the authors have any competing interests to declare. 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.

Incidence and familial risk of premature ovarian insufficiency in the Finnish female population.

STUDY QUESTION: What is the incidence of premature ovarian insufficiency (POI), has the incidence of POI changed over time, and what is the risk of POI among relatives of POI women? SUMMARY ANSWER: The incidence of POI increased among females aged 15-19 years from 2007 onwards and decreased in older age groups, and among relatives of women with POI the risk of POI is significantly increased. WHAT IS KNOWN ALREADY: So far, there has been no good quality, nationwide studies of the incidence of POI. Early menopause has been associated with the elevated risk of early menopause among relatives, but the knowledge of the familial risk of POI is scarce. Lower socioeconomic status has been associated with lower age at natural menopause. STUDY DESIGN, SIZE, DURATION: Population-based study with 5011 women diagnosed with POI in 1988-2017. The data were collected from national registries and covers POI subjects in entire Finland. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with hormone replacement therapy reimbursement for POI were identified from Social Insurance Institution (SII). We calculated POI incidence in different age groups and studied the changes in the incidence rate over time in 5-year segments. Four population-based controls were selected from the Digital and Population Data Services Agency (DVV) for each POI woman. Family members of the POI cases and controls were identified from the DVV and linked to SII reimbursement data to identify POI diagnoses among them. The familial risk of POI was estimated with a logistical regression model. MAIN RESULTS AND THE ROLE OF CHANCE: The incidence was highest in the 35-39 age group, ranging from 73.8/100 000 women-years in 1993-1997 to 39.9/100 000 women-years in 2013-2017. From 2007, the incidence among 15- to 19-year-olds rose from 7.0 to 10.0/100 000 women-years in 2015-2017. Cumulative incidence of POI for women under 40 years in 1988-2017 was 478/100 000 women. The relative risk of POI among relatives of women with POI was 4.6 (95% CI 3.3-6.5) compared to relatives of women without POI. POI women tended to have slightly lower socioeconomic status and level of education compared to controls. LIMITATIONS, REASONS FOR CAUTION: For some women with POI, diagnosis or reimbursement may be lacking. However, we presume that these women represent a minority due to the nature of the disease and the economic benefits of reimbursement. Some changes in the incidence of POI can reflect changes in clinical practice and changing treatments and reimbursement criteria. WIDER IMPLICATIONS OF THE FINDINGS: The risk of developing POI is significantly higher in women who have first-degree relatives diagnosed with POI. Raising awareness of the increased risk might lead to earlier diagnosis and initiation of hormonal replacement therapy, possibly preventing adverse effects of low oestrogen levels, such as osteoporosis. STUDY FUNDING/COMPETING INTEREST(S): This work was financially supported by the Oulu University Hospital. H.S. received a grant from Finnish Menopause Society. S.M.S. received a grant from the Finnish Menopause Society, the Finnish Medical Foundation and the Juho Vainio Foundation. The authors do not have any competing interests to declare. 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.

Using Robson's Ten-Group Classification System for comparing caesarean section rates in Europe: an analysis of routine data from the Euro-Peristat study.

OBJECTIVE: Robson's Ten Group Classification System (TGCS) creates clinically relevant sub-groups for monitoring caesarean birth rates. This study assesses whether this classification can be derived from routine data in Europe and uses it to analyse national caesarean rates. DESIGN: Observational study using routine data. SETTING: Twenty-seven EU member states plus Iceland, Norway, Switzerland and the UK. POPULATION: All births at ≥22 weeks of gestational age in 2015. METHODS: National statistical offices and medical birth registers derived numbers of caesarean births in TGCS groups. MAIN OUTCOME MEASURES: Overall caesarean rate, prevalence and caesarean rates in each of the TGCS groups. RESULTS: Of 31 countries, 18 were able to provide data on the TGCS groups, with UK data available only from Northern Ireland. Caesarean birth rates ranged from 16.1 to 56.9%. Countries providing TGCS data had lower caesarean rates than countries without data (25.8% versus 32.9%, P = 0.04). Countries with higher caesarean rates tended to have higher rates in all TGCS groups. Substantial heterogeneity was observed, however, especially for groups 5 (previous caesarean section), 6, 7 (nulliparous/multiparous breech) and 10 (singleton cephalic preterm). The differences in percentages of abnormal lies, group 9, illustrate potential misclassification arising from unstandardised definitions. CONCLUSIONS: Although further validation of data quality is needed, using TGCS in Europe provides valuable comparator and baseline data for benchmarking and surveillance. Higher caesarean rates in countries unable to construct the TGCS suggest that effective routine information systems may be an indicator of a country's investment in implementing evidence-based caesarean policies. TWEETABLE ABSTRACT: Many European countries can provide Robson's Ten-Group Classification to improve caesarean rate comparisons.

Associations between interpregnancy interval and preterm birth by previous preterm birth status in four high-income countries: a cohort study.

OBJECTIVE: To investigate the effect of interpregnancy interval (IPI) on preterm birth (PTB) according to whether the previous birth was preterm or term. DESIGN: Cohort study. SETTING: USA (California), Australia, Finland, Norway (1980-2017). POPULATION: Women who gave birth to first and second (n = 3 213 855) singleton livebirths. METHODS: Odds ratios (ORs) for PTB according to IPIs were modelled using logistic regression with prognostic score stratification for potential confounders. Within-site ORs were pooled by random effects meta-analysis. OUTCOME MEASURE: PTB (gestational age <37 weeks). RESULTS: Absolute risk of PTB for each IPI was 3-6% after a previous term birth and 17-22% after previous PTB. ORs for PTB differed between previous term and preterm births in all countries (P-for-interaction ≤ 0.001). For women with a previous term birth, pooled ORs were increased for IPI <6 months (OR 1.50, 95% CI 1.43-1.58); 6-11 months (OR 1.10, 95% CI 1.04-1.16); 24-59 months (OR 1.16, 95% CI 1.13-1.18); and ≥ 60 months (OR 1.72, 95%CI 1.60-1.86), compared with 18-23 months. For previous PTB, ORs were increased for <6 months (OR 1.30, 95% CI 1.18-1.42) and ≥60 months (OR 1.29, 95% CI 1.17-1.42), but were less than ORs among women with a previous term birth (P < 0.05). CONCLUSIONS: Associations between IPI and PTB are modified by whether or not the previous pregnancy was preterm. ORs for short and long IPIs were higher among women with a previous term birth than a previous PTB, which for short IPI is consistent with the maternal depletion hypothesis. Given the high risk of recurrence and assuming a causal association between IPI and PTB, IPI remains a potentially modifiable risk factor for women with previous PTB. TWEETABLE ABSTRACT: Short versus long interpregnancy intervals associated with higher ORs for preterm birth (PTB) after a previous PTB.

Pregnancy, delivery and postpartum in women with schizophrenia or schizoaffective disorder in Finland: a national register-based comparative study.

As part of anational Finnish study on reproductive health of women with severe mental disorders, we compared pregnancy- and delivery-, and postpartum-related outcomes between women with schizophrenia (n = 3444) and those with schizoaffective disorder (n = 985), focusing on their singleton pregnancies after illness onset (n = 708 and n = 242, respectively). For comparison, data also included 22,101 controls with 3668 pregnancies. The Finnish Medical Birth Register, the Register of Congenital Malformations and the Child Welfare Register were used. Despite known differences between the two disorders, we found no robust differences between these patient groups.

Timing of paediatric orchidopexy in universal healthcare systems: international administrative data cohort study.

BACKGROUND: International guidelines in 2008 recommended orchidopexy for undescended testis at 6-12 months of age to reduce the risk of testicular cancer and infertility. Using administrative data from England, Finland, Ontario (Canada), Scotland and Sweden (with data from Victoria (Australia) and Iceland in supplementary analyses), the aim of this study was to investigate compliance with these guidelines and identify potential socioeconomic inequities in the timing of surgery before 1 and 3 years. METHODS: All boys born in 2003-2011 with a diagnosis code of undescended testis and procedure codes indicating orchidopexy before their fifth birthday were identified from administrative health records. Trends in the proportion of orchidopexies performed before 1 and 3 years of age were investigated, as were socioeconomic inequities in adherence to the guidelines. RESULTS: Across all jurisdictions, the proportion of orchidopexies occurring before the first birthday increased over the study period. By 2011, from 7·6 per cent (Sweden) to 27·9 per cent (Scotland) of boys had undergone orchidopexy by their first birthday and 71·5 per cent (Sweden) to 90·4 per cent (Scotland) by 3 years of age. There was limited evidence of socioeconomic inequities for orchidopexy before the introduction of guidelines (2008). Across all jurisdictions for boys born after 2008, there was consistent evidence of inequities in orchidopexy by the first birthday, favouring higher socioeconomic position. Absolute differences in these proportions between the highest and lowest socioeconomic groups ranged from 2·5 to 5·9 per cent across jurisdictions. CONCLUSION: Consistent lack of adherence to the guidelines across jurisdictions questions whether the guidelines are appropriate.

ANTECEDENTES: En el 2008, las guías internacionales recomendaban efectuar una orquidopexia para los testículos no descendidos entre los seis y los 12 meses de edad para reducir los riesgos de cáncer testicular e infertilidad. Utilizando datos administrativos de Inglaterra, Finlandia, Ontario (Canadá), Escocia y Suecia (con datos de Victoria, Australia e Islandia para análisis complementarios), el objetivo de este estudio fue investigar el cumplimiento de estas guías y la identificación de posibles desigualdades socioeconómicas con relación al momento de la cirugía antes de 1 y 3 años de edad. MÉTODOS: A partir de los registros administrativos de salud, se identificaron todos los niños nacidos entre 2003 y 2011 con código diagnóstico de testículos no descendidos y con código de procedimiento correspondiente a orquidopexia antes de cumplir 5 años. Se investigaron las tendencias en la proporción de orquidopexias realizadas antes de 1 y 3 años de edad, respectivamente, al igual que las desigualdades socioeconómicas en el cumplimiento de las directrices de las guías. RESULTADOS: En todas las jurisdicciones, la proporción de orquidopexias realizadas antes del primer año de vida aumentó durante el periodo de estudio. En 2011, del 7,6% (Suecia) al 27,9% (Escocia) de los niños habían sido sometidos a orquidopexia en su primer año de vida y del 71,5% (Suecia) al 90,4% (Escocia) a los 3 años de edad. Hubo evidencia limitada de las inequidades socioeconómicas para la orquidopexia antes de la introducción de las guías (2008). En todas las jurisdicciones para los niños nacidos después de 2008, hubo evidencia consistente de inequidades para la práctica de una orquidopexia en el primer año de vida en favor de una posición socioeconómica más alta (socioeconomic position, SEP). Las diferencias absolutas en estas proporciones entre los grupos SEP más altos y más bajos oscilaron entre el 2,5% y el 5,9% en todas las jurisdicciones. CONCLUSIÓN: La falta de adherencia a las guías observada consistentemente en todas las jurisdicciones cuestiona si las guías son apropiadas.

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.

The overall and sex- and age-group specific incidence rates of cancer in people with schizophrenia: a population-based cohort study.

AIMS: Decades of research show that people with schizophrenia have an increased risk of death from cancer; however, the relationship between schizophrenia and cancer incidence remains less clear. This population-based study investigates the incidence of seven common types of cancer among people with a hospital diagnosis of schizophrenia and accounting for the effects of age, sex and calendar time. METHODS: This population-based study used 1990-2013 data from three nationwide Swedish registries to calculate the incidence (in total, by age group and by sex) of any cancer and of lung, oesophageal, pancreatic, stomach, colon, (in men) prostate and (in women) breast cancer in 111 306 people with a hospital diagnosis of schizophrenia. The incidence in people with diagnosed schizophrenia was compared with the incidence in the general population. Risk estimates accounted for the effects of calendar time. RESULTS: In 1 424 829 person-years of follow-up, schizophrenia did not confer an overall higher cancer risk (IRR 1.02, 95% CI 0.91-1.13) but was associated with a higher risk for female breast (IRR 1.19, 95% CI 1.12-1.26), lung (IRR 1.42, 95% CI 1.28-1.58), oesophageal (IRR 1.25, 95% CI 1.07-1.46) and pancreatic (IRR 1.10, 95% CI 1.01-1.21) and a lower risk of prostate (IRR 0.66, 95% CI 0.55-0.79) cancer. Some age- and sex-specific differences in risk were observed. CONCLUSIONS: People with schizophrenia do not have a higher overall incidence of cancer than people in the general population. However, there are significant differences in the risk of specific cancer types overall and by sex calling for efforts to develop disease-specific prevention programmes. In people with schizophrenia, higher risk generally occurs in those <75 years.

Anaphylaxis in pregnancy: a population-based multinational European study.

Anaphylaxis in pregnancy is a rare but severe complication for both mother and infant. Population-based data on anaphylaxis in pregnancy are lacking from mainland European countries. This multinational study presents the incidence, causative agents, management and maternal and infant outcomes of anaphylaxis in pregnancy. This descriptive multinational study used a combination of retrospective (Finnish medical registries) and prospective population-based studies (UK, France, Belgium and the Netherlands) to identify cases of anaphylaxis. Sixty-five cases were identified among 4,446,120 maternities (1.5 per 100,000 maternities; 95%CI 1.1-1.9). The incidence did not vary between countries. Approximately three-quarters of reactions occurred at the time of delivery. The most common causes were antibiotics in 27 women (43%), and anaesthetic agents in 11 women (17%; including neuromuscular blocking drugs, 7), which varied between countries. Anaphylaxis had very poor outcomes for one in seven mothers and one in seven babies; the maternal case fatality rate was 3.2% (95%CI 0.4-11.0) and the neonatal encephalopathy rate was 14.3% (95%CI 4.8-30.3). Across Europe, anaphylaxis related to pregnancy is rare despite having a multitude of causative agents and different antibiotic prophylaxis protocols.

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.