Birth size after embryo cryopreservation: larger by all measures?

STUDY QUESTION: Are the changes in birthweight after frozen and fresh embryo transfer associated with corresponding changes in other measures of foetal growth and placental efficiency? SUMMARY ANSWER: Although placental efficiency was reduced for both frozen and fresh embryo transfer, children born after frozen embryo transfer (frozen-ET) had symmetrically increased size at birth, whereas children born after fresh embryo transfer (fresh-ET) were asymmetrically smaller at birth, compared to naturally conceived children. WHAT IS KNOWN ALREADY: In pregnancies following frozen-ET, the risk of being born large, as measured by birthweight, is higher than after natural and fresh-ET conceptions. It is not known whether this is a result of symmetrically increased growth and increased placental efficiency. STUDY DESIGN, SIZE, DURATION: A Norwegian nationwide registry-based cohort study of 3093 singletons born after frozen-ET, 15 510 singletons born after fresh-ET and 1 125 366 singletons born after natural conception from 1988 to 2015 was performed. We identified 6334 sibships with at least two different conception methods. PARTICIPANTS/MATERIALS, SETTING, METHODS: Data were collected from the Medical Birth Registry of Norway and the Norwegian National Education Database. Main outcome measures were birth length, birthweight, head circumference, ponderal index (birthweight relative to birth length in kg/m3), placental weight, birthweight:placental weight ratio, gestational age, and birthweight z-score. We estimated mean differences between children born after frozen-ET and fresh-ET compared to natural conception, at the population level and within sibships. Adjustments were made for birth year, maternal age, parity, and education. MAIN RESULTS AND THE ROLE OF CHANCE: Estimates at the population level and within sibships were consistent for all outcomes, for both fresh and frozen-ET compared to natural conception. Within sibships, children born after frozen-ET had longer mean length (Δ = 0.42 cm, 95% CI 0.29 to 0.55) and head circumference (Δ = 0.32 cm, 95% CI 0.23 to 0.41) at birth, but a similar ponderal index (Δ = 0.11 kg/m3, 95% CI -0.04 to 0.26), compared to naturally conceived. Children born after fresh-ET had a shorter length (Δ = -0.22 cm, 95% CI -0.29 to -0.15) and head circumference (Δ = -0.15 cm, 95% CI -0.19 to -0.10), and lower ponderal index (Δ = -0.15 kg/m3, 95% CI -0.23 to -0.07) at birth compared to natural conception within sibships. Furthermore, mean placental weight was larger after both frozen-ET (Δ = 37 g, 95% CI 28 to 45) and fresh-ET (Δ = 7 g, 95% CI 2 to 13) compared to natural conception within sibships, whereas mean birthweight:placental weight ratio was reduced for both frozen-ET (Δ = -0.11, 95% CI -0.17 to -0.05) and fresh-ET (Δ = -0.13, 95% CI -0.16 to -0.09). A range of sensitivity analyses all gave similar conclusions as the main models, including restriction to full siblings, restriction to single embryo transfer, and adjustment for maternal BMI, height, and smoking. LIMITATIONS, REASONS FOR CAUTION: Additional adjustment for maternal BMI, height, and smoking was possible only for a small sample of the study population (15%). Data on causes and duration of infertility, as well as treatment details, were limited. WIDER IMPLICATIONS OF THE FINDINGS: The increased birthweight observed in singletons after frozen-ET is associated with a symmetrically increased birth size and large placentas, also after controlling for maternal factors through sibship analyses. Identifying the responsible treatment factors and the long-term health outcomes are particularly important considering the increase in elective freezing of all embryos. STUDY FUNDING/COMPETING INTEREST(S): This work was partly supported by the Central Norway Regional Health Authorities (project number 46045000), the Norwegian University of Science and Technology (project number 81850092) and the Research Council of Norway through its Centres of Excellence funding scheme (project number 262700). The authors have no conflicts of interest 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.

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.

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

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

T-cell acute lymphoblastic leukemia in patients 1-45 years treated with the pediatric NOPHO ALL2008 protocol.

The NOPHO ALL2008 is a population-based study using an unmodified pediatric protocol in patients 1-45 years of age with acute lymphoblastic leukemia. Patients with T-ALL were given a traditional pediatric scheme if fast responding (minimal residual disease (MRD) < 0.1% day 29), or intensive block-based chemotherapy if slow responding (MRD > 0.1% day 29). Both treatment arms included pediatric doses of high-dose methotrexate and asparaginase. If MRD ≥ 5% on day 29 or ≥0.1% after consolidation, patients were assigned to allogeneic hematopoietic stem cell transplantation. The 5-year overall survival of the 278 T-ALL patients was 0.75 (95% CI 0.69-0.81), being 0.82 (0.74-0.88) for patients 1.0-9.9 years, 0.76 (0.66-0.86) for those 10.0-17.9 years, and 0.65 (0.55-0.75) for the older patients. The risk of death in first remission was significantly higher in adults (12%) compared with the 1-9 years group (4%). The MRD responses in the three age groups were similar, and only a nonsignificant increase in relapse risk was found in adults. In conclusion, an unmodified pediatric protocol in patients 1-45 years is effective in all age groups. The traditional pediatric treatment schedule was safe for all patients, but the intensive block therapy led to a high toxic death rate in adults.

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.

TOP2A gene copy number change in breast cancer.

AIMS: The clinical significance of TOP2A as a prognostic marker has not been clarified. The aims of this study were to investigate the frequency of TOP2A copy number change; to correlate TOP2A with HER2 status, hormone receptor (HR) status and molecular subtype, and further to explore differences in breast cancer-specific survival according to TOP2A and HER2. METHODS: In this study, TOP2A, HER2 and chromosome 17 copy number were assessed in 670 cases of breast cancer using in situ hybridisation techniques. Gene to chromosome ratios ≥2 were classified as amplification. TOP2A deletion (gene to chromosome ratio ≤0.8) or monosomy (only one signal for both gene and chromosome in more than 75% of nuclei) were classified as gene loss. RESULTS: A strong association between TOP2A change and HR and HER2 status was found. During the first 5 years after diagnosis, the risk of death from breast cancer was significantly higher for cases with HER2 amplification irrespective of TOP2A status. CONCLUSIONS: TOP2A copy number change was strongly associated with HR and HER2 status and as a prognostic marker TOP2A is probably of limited value.

Molecular subtypes, histopathological grade and survival in a historic cohort of breast cancer patients.

Molecular subtyping of breast cancer may provide additional prognostic information regarding patient outcome. However, its clinical significance remains to be established. In this study, the main aims were to discover whether reclassification of breast cancer into molecular subtypes provides more precise information regarding outcome compared to conventional histopathological grading and to study breast cancer-specific survival in the different molecular subtypes. Cases of breast cancer occurring in a cohort of women born between 1886 and 1928 with long-term follow-up were included in the study. Tissue microarrays were constructed from archival formalin-fixed, paraffin-embedded tissue from 909 cases. Using immunohistochemistry and in situ hybridisation as surrogates for gene expression analyses, all cases were reclassified into the following molecular subtypes: Luminal A; Luminal B (HER2-); Luminal B (HER2+); HER2 subtype; Basal phenotype; and five negative phenotype. Kaplan-Meier survival curves and Cox proportional hazards models were used in the analyses. During the first 5 years after diagnosis, there were significant differences in prognosis according to molecular subtypes with the best survival for the Luminal A subtype and the worst for HER2 and five negative phenotype. In this historic cohort of women with breast cancer, differences in breast cancer-specific survival according to subtype occur almost exclusively amongst the histopathological grade 2 tumours. From 5 years after time of diagnosis until the end of follow-up, there appears to be no difference in survival according to molecular subtype or histopathological grade.

Weight change in adulthood and risk of postmenopausal breast cancer: the HUNT study of Norway.

BACKGROUND: Adult weight gain is associated with increased risk of postmenopausal breast cancer. Most previous studies are limited by using recalled or self-reported data, and it is not known if age-specific weight changes are important for breast cancer risk. METHODS: In a Norwegian cohort of 28,153 women (and 900 incident breast cancers) with longitudinal anthropometric measurements over up to 30 years, we studied both overall and age-related weight changes in adulthood and risk of postmenopausal breast cancer. RESULTS: Overall, weight gain in adulthood was associated with increased breast cancer risk (hazard ratio (HR) per kg per year 1.31, 95% confidence interval (CI) 1.11-1.54). Weight gain before (HR per kg per year 1.38, 95% CI 1.09-1.75) or around menopause (1.69, 95% CI 1.32-2.16) was associated with increased risk, but there was no clear risk increase associated with later weight gain (HR per kg per year 0.92, 95% CI 0.73-1.18). CONCLUSION: Weight gain in adulthood was associated with increased risk of breast cancer. Our results suggest that weight gain before and around menopausal age may be particularly important for breast cancer risk among postmenopausal women.

Hypertensive diseases in pregnancy and breast cancer risk.

BACKGROUND: Hypertensive diseases in pregnancy may be associated with a reduced risk of breast cancer. Most previous studies are small and have shown conflicting results. METHODS: In a cohort of 919 712 women who gave their first birth between 1967 and 2008, with linkage of information from two national registries, we assessed whether women with pregnancy hypertensive diseases are at reduced breast cancer risk. We used Cox regression to estimate hazard ratios (HRs) with 95% confidence intervals (CI). RESULTS: Compared with women with a normotensive first pregnancy, women with hypertension or preeclampsia in their first pregnancy had a reduced breast cancer risk (HR 0.83, 95% CI 0.77, 0.90). A reduced risk was consistently observed for hypertensive disease in any pregnancy, for recurrent hypertensive disease in pregnancy, and before and after 50 years of age at breast cancer diagnosis. The association was strongest for women with hypertension in pregnancy, who delivered at term/post-term (HR 0.81, 95% CI 0.75, 0.88) or had a child of average birth weight (HR 0.77, 95% CI 0.69, 0.85). CONCLUSION: Women with pregnancy hypertensive diseases are at reduced breast cancer risk. Whether this association can be attributed to pregnancy-specific events or to underlying biological traits remains unclear.

Joint effects of nulliparity and other breast cancer risk factors.

BACKGROUND: Pregnancy may reduce breast cancer risk through induction of persistent changes of the mammary gland that make the breast less susceptible to carcinogenic factors. It is not known to what extent the effects of parity are independent of other breast cancer risk factors. METHODS: In a Norwegian cohort of 58 191 women (2890 breast cancers), we assessed whether the effects of parity on postmenopausal breast cancer risk may be modified by menstrual and anthropometric factors. We calculated attributable proportions due to interaction as a measure of synergism. RESULTS: Parity, height, body mass index (BMI), age at menarche and menopause were all associated with breast cancer risk in the expected directions. For BMI, follow-up was stratified into two age groups because of non-proportional hazards. We found that nulliparity and overweight may amplify each other's effect on breast cancer risk among women after 70 years of age (attributable proportion 0.21, 95% confidence interval 0.04-0.39). There was some indication that parity and age at menopause may antagonise each other's effect. Effects of parity were largely unaffected by age at menarche and height. CONCLUSION: Nulliparity and overweight may have a synergistic effect on breast cancer risk in elderly women. If confirmed by others, the findings may help disentangle the interplay of different causes of breast cancer.

Association of size at birth with adolescent hormone levels, body size and age at menarche: relevance for breast cancer risk.

Birth size has been positively associated with age at menarche and height in adolescence and adulthood, but the relevant biological mechanisms remain unclear. Among 262 Norwegian term-born singleton girls, birth size measures (weight, length, ponderal index, head circumference and subscapular skin-fold thickness) were analysed in relation to adolescent hormone levels (oestradiol, prolactin, dehydroepiandrosterone sulphate, androstenedione and free testosterone index), age at menarche and adolescent (ages 12.7-15.5 years) and body size (height, weight, body mass index and waist-to-hip ratio) using survival analysis and general linear modelling. The results were adjusted for gestational age at birth, age and menarcheal status at measurement in adolescence and maternal age at menarche. Birth weight, birth length and head circumference were positively associated with adolescent weight and height, and small birth size was associated with earlier age at menarche. Subscapular skin-fold thickness at birth was not associated with adolescent body size, but low fold-thickness was associated with earlier age at menarche. Measures of birth size were inversely related to circulating levels of dehydroepiandrosterone sulphate in adolescence, but there was no clear association with other hormones. These results suggest that physical and sexual development in puberty and adolescence is influenced by prenatal factors, and in combination, these factors may influence health and disease later in life.

Response rates with different distribution methods and reward, and reproducibility of a quantitative food frequency questionnaire.

OBJECTIVES: To evaluate the use of a self-administered quantitative food frequency questionnaire (QFFQ) in a national dietary survey concerning (a) response rates with different distribution methods and reward; (b) degree of underreporting of energy intake; (c) reproducibility of the QFFQ; and (d) seasonal variation on reported intake. DESIGN AND SUBJECTS: A pilot study was performed in 1992 to test response rates to the QFFQ with three different distribution methods, with and without reward, in a random sample of 1200 adults aged 16-79 y. In another study, the QFFQ was distributed to a nation-wide, representative random sample of 5008 adults aged 16-79 y during June, September, November 1993 and March 1994. Reproducibility was evaluated among 90 responders to the survey who answered another QFFQ six weeks later. RESULTS: The distribution method combining postal distribution and collecting the QFFQ by interviewer as well as an offer to participate in a lottery, gave the highest response rate (72%). The possibility to get a reward increased the response rate by 9, 14 and 57%, respectively, depending on the distribution method used. The mean daily energy intake and the percentage of subjects claiming to have unlikely low energy intake did not differ significantly between the different ways of distribution. In the main survey the mean ratio between energy intake and estimated basal metabolic rate was 1.58 among men and 1.47 among women, and 37% of men and 45% of women had a ratio below 1.35. Spearman rank correlations between the two QFFQ ranged from 0.48 (edible fats) to 0.91 (coffee) with a median coefficient of 0.70. For nutrients correlations ranged from 0.55 (carbohydrate E%) to 0.81 (alcohol), with a median coefficient of 0.72. The season of questionnaire administration was of minor importance for the reported intake of the main foods and nutrients. CONCLUSIONS: The QFFQ-method is suitable for use in a Norwegian nutritional surveillance system. SPONSORSHIP: National Nutrition Council, Ministry for Agriculture, Ministry for Health and Social Affairs and Norwegian Research Council.