Neonatal outcomes in singleton pregnancies conceived by fresh or frozen embryo transfer compared to spontaneous conceptions: a systematic review and meta-analysis

Change of HeART: Cardiovascular Implications of Assisted Reproductive Technology

Cardiovascular (CV) disease is the leading cause of death in women, and it may manifest differently than in men, in part related to sex-specific CV risk factors. In females, assisted reproductive technologies (ARTs) are commonly used to treat infertility, and they utilize controlled ovarian stimulation involving the administration of exogenous sex hormones. ARTs, and especially controlled ovarian stimulation, have been associated with an increased pregnancy and short-term CV risk, although the long-term CV implications of these treatments in individuals treated with ARTs and their offspring remain unclear. This review endeavors to provide a comprehensive examination of what is known about the relationship between ART and CV outcomes for females treated with ARTs, as well as their offspring, and recommendations for future research. Novel insights into female-specific CV risk factors are critical to reduce the disproportionate burden of CV disease in Canadian women. ART has revolutionized reproductive medicine, offering hope to millions of individuals with infertility worldwide, and a further understanding of the CV implications of this important sex-specific CV risk factor is warranted urgently.

Modified natural cycle allows a window of 7 days for frozen embryo transfer planning

RESEARCH QUESTION

Should ovulation be triggered in a modified natural cycle (mNC) with recombinant human chorionic gonadotrophin (rHCG) as soon as a mean follicle diameter of 17 mm is visible, or is more flexible planning possible?

DESIGN

This multicentre, retrospective, observational study of 3087 single frozen blastocyst transfers in mNC was carried out between January 2020 and September 2022. The inclusion criteria included endometrial thickness ≥7 mm and serum progesterone <1.5 ng/ml. The main outcome was ongoing pregnancy rate. Secondary end-points were pregnancy rate, implantation rate, clinical pregnancy rate and miscarriage rate. The mean follicle size at triggering was stratified into three groups (13.0-15.9, 16.0-18.9 and 19.0-22 mm).

RESULTS

The baseline characteristics between the groups did not vary significantly for age, body mass index and the donor's age for egg donation. No differences were found in pregnancy rate (64.5%, 60.2% and 57.4%; P = 0.19), clinical pregnancy rate (60.5%, 52.8% and 50.6%; P = 0.10), implantation rate (62.10%, 52.9% and 51.0%; P = 0.05) or miscarriage rate (15.0%, 22.2%; and 25.0%; P = 0.11). Although ongoing pregnancy rate (54.9%, 46.8% and 43.1%; P = 0.02) varied significantly in the univariable analysis, it was no longer significant after adjustment for the use of preimplantation genetic testing for aneuploidies and egg donation.

CONCLUSIONS

The findings showed rHCG could be flexibly administered with a mean follicle size between 13 and 22 mm as long as adequate endometrial characteristics are met, and serum progesterone is <1.5 ng/ml. Considering the follicular growth rate of 1-1.5 mm/day, this approach could allow a flexibility for FET scheduling of 6-7 days, simplifying mNC FET planning in clinical practice.

No major differences in perinatal and maternal outcomes between uninterrupted embryo culture in time-lapse system and conventional embryo culture

STUDY QUESTION

Is embryo culture in a closed time-lapse system associated with any differences in perinatal and maternal outcomes in comparison to conventional culture and spontaneous conception?

SUMMARY ANSWER

There were no significant differences between time-lapse and conventional embryo culture in preterm birth (PTB, <37 weeks), low birth weight (LBW, >2500 g) and hypertensive disorders of pregnancy for singleton deliveries, the primary outcomes of this study.

WHAT IS KNOWN ALREADY

Evidence from prospective trials evaluating the safety of time-lapse incubation for clinical use show similar embryo development rates, implantation rates, and ongoing pregnancy and live birth rates when compared to conventional incubation. Few studies have investigated if uninterrupted culture can alter risks of adverse perinatal outcomes presently associated with IVF when compared to conventional culture and spontaneous conceptions.

STUDY DESIGN, SIZE, DURATION

This study is a Swedish population-based retrospective registry study, including 7379 singleton deliveries after fresh embryo transfer between 2013 and 2018 from selected IVF clinics. Perinatal outcomes of singletons born from time-lapse-cultured embryos were compared to singletons from embryos cultured in conventional incubators and 71 300 singletons from spontaneous conceptions. Main perinatal outcomes included PTB and LBW. Main maternal outcomes included hypertensive disorders of pregnancy (pregnancy hypertension and preeclampsia).

PARTICIPANTS/MATERIALS, SETTING, METHODS

From nine IVF clinics, 2683 singletons born after fresh embryo transfer in a time-lapse system were compared to 4696 singletons born after culture in a conventional incubator and 71 300 singletons born after spontaneous conception matched for year of birth, parity, and maternal age. Patient and treatment characteristics from IVF deliveries were cross-linked with the Swedish Medical Birth Register, Register of Birth Defects, National Patient Register and Statistics Sweden. Children born after sperm and oocyte donation cycles and after Preimplantation Genetic testing cycles were excluded. Odds ratio (OR) and adjusted OR were calculated, adjusting for relevant confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

In the adjusted analyses, no significant differences were found for risk of PTB (adjusted OR 1.11, 95% CI 0.87-1.41) and LBW (adjusted OR 0.86, 95% CI 0.66-1.14) or hypertensive disorders of pregnancy; preeclampsia and hypertension (adjusted OR 0.99, 95% CI 0.67-1.45 and adjusted OR 0.98, 95% CI 0.62-1.53, respectively) between time-lapse and conventional incubation systems. A significantly increased risk of PTB (adjusted OR 1.31, 95% CI 1.08-1.60) and LBW (adjusted OR 1.36, 95% CI 1.08-1.72) was found for singletons born after time-lapse incubation compared to singletons born after spontaneous conceptions. In addition, a lower risk for pregnancy hypertension (adjusted OR 0.72 95% CI 0.53-0.99) but no significant difference for preeclampsia (adjusted OR 0.87, 95% CI 0.68-1.12) was found compared to spontaneous conceptions. Subgroup analyses showed that some risks were related to the day of embryo transfer, with more adverse outcomes after blastocyst transfer in comparison to cleavage stage transfer.

LIMITATIONS, REASONS FOR CAUTION

This study is retrospective in design and different clinical strategies may have been used to select specific patient groups for time-lapse versus conventional incubation. The number of patients is limited and larger datasets are required to obtain more precise estimates and adjust for possible effect of additional embryo culture variables.

WIDER IMPLICATIONS OF THE FINDINGS

Embryo culture in time-lapse systems is not associated with major differences in perinatal and maternal outcomes, compared to conventional embryo culture, suggesting that this technology is an acceptable alternative for embryo incubation.

STUDY FUNDING/COMPETING INTEREST(S)

The study was financed by a research grant from Gedeon Richter. There are no conflicts of interest for all authors to declare.

TRIAL REGISTRATION NUMBER

N/A.

Infertility and Risk of Autism Spectrum Disorder in Children

Importance

Previous studies on the risk of childhood autism spectrum disorder (ASD) following fertility treatment did not account for the infertility itself or the mediating effect of obstetrical and neonatal factors.

Objective

To assess the association between infertility and its treatments on the risk of ASD and the mediating effect of selected adverse pregnancy outcomes on that association.

Design, Setting, and Participants

This was a population-based cohort study in Ontario, Canada. Participants were all singleton and multifetal live births at 24 or more weeks' gestation from 2006 to 2018. Data were analyzed from October 2022 to October 2023.

Exposures

The exposure was mode of conception, namely, (1) unassisted conception, (2) infertility without fertility treatment (ie, subfertility), (3) ovulation induction (OI) or intrauterine insemination (IUI), or (4) in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).

Main Outcome and Measures

The study outcome was a diagnosis of ASD at age 18 months or older. Cox regression models generated hazard ratios (HR) adjusted for maternal and infant characteristics. Mediation analysis further accounted for the separate effect of (1) preeclampsia, (2) cesarean birth, (3) multifetal pregnancy, (4) preterm birth at less than 37 weeks, and (5) severe neonatal morbidity.

Results

A total of 1 370 152 children (703 407 male [51.3%]) were included: 1 185 024 (86.5%) with unassisted conception, 141 180 (10.3%) with parental subfertility, 20 429 (1.5%) following OI or IUI, and 23 519 (1.7%) following IVF or ICSI. Individuals with subfertility or fertility treatment were older and resided in higher-income areas; the mean (SD) age of each group was as follows: 30.1 (5.2) years in the unassisted conception group, 33.3 (4.7) years in the subfertility group, 33.1 (4.4) years in the OI or IUI group, and 35.8 (4.9) years in the IVF or ICSI group. The incidence rate of ASD was 1.93 per 1000 person-years among children in the unassisted conception group. Relative to the latter, the adjusted HR for ASD was 1.20 (95% CI, 1.15-1.25) in the subfertility group, 1.21 (95% CI, 1.09-1.34) following OI or IUI, and 1.16 (95% CI, 1.04-1.28) after IVF or ICSI. Obstetrical and neonatal factors appeared to mediate a sizeable proportion of the aforementioned association between mode of conception and ASD risk. For example, following IVF or ICSI, the proportion mediated by cesarean birth was 29%, multifetal pregnancy was 78%, preterm birth was 50%, and severe neonatal morbidity was 25%.

Conclusions and Relevance

In this cohort study, a slightly higher risk of ASD was observed in children born to individuals with infertility, which appears partly mediated by certain obstetrical and neonatal factors. To optimize child neurodevelopment, strategies should further explore these other factors in individuals with infertility, even among those not receiving fertility treatment.

Limited Effects of Ultra-low Oxygen Concentration during Extended Embryo Culture on In vitro Fertilisation Outcomes in Indian Women: A Retrospective Cross-sectional Study

Background

Amongst various other factors, oxygen (O2) concentration in embryo culture plays an important role in determining pregnancy outcomes in women undergoing in vitro fertilisation. Some studies have reported that lowering O2 levels in embryo culture provides better results.

Aims

To explore the effects of low- and ultra-low- O2 concentrations (5% and 2%, respectively) in extended embryo culture on various outcome parameters of pregnancy.

Settings and Design

This was a retrospective cross-sectional study.

Materials and Methods

In this study 382 participants had their embryos cultured in varying O2 concentrations (5% or 2%), followed by either a fresh embryo transfer (ET) or frozen embryo transfer (FET). Outcomes such as pregnancy rate, implantation rate, abortion rate, twinning rate, and live birth rate were compared between the groups.

Statistical Analysis Used

Chi square test was applied to compare the primary and secondary outcomes between different groups.

Results

No significant differences were observed in pregnancy rate and implantation rate between 5% and 2% O2 groups, irrespective of their mode of ET. The abortion rate was significantly higher in 5% O2 group than in 2% group during FET (24.71% vs. 11.49%, P = 0.02). While the proportion of good-quality embryos was higher in 5% O2 group, these did not translate to better pregnancy outcomes. Additionally, embryos cultured in 2% O2 concentration had a significantly better implantation rate when they were transferred fresh rather than frozen (71.34% vs. 61.46%, P = 0.04). There were no other differences observed.

Conclusion

Only marginal benefits were observed in switching human embryos to ultra-low O2 concentration after the initial days of culture.

Perinatal Outcome of Singletons Born after Using a Simplified Low-Cost IVF Culture System and All Singletons Born in Flanders (Belgium) between 2012 and 2020

BACKGROUND

We developed a simplified IVF culture system (SCS) which has proven to be effective and safe in a selected IVF cohort.

METHODS

Preterm birth (PTB) and low birth weight (LBW) of 175 singletons born after using the SCS, 104 after fresh embryo transfer (ET), and 71 after frozen embryo transfer, were compared with all singletons born in Flanders between 2012 and 2020 conceived after natural conception, ovarian stimulation (OS), and assisted reproduction (IVF/ICSI).

FINDINGS

The proportion of preterm (<37 weeks) births was significantly higher in the case of IVF or ICSI, followed by hormonal treatment, compared to spontaneous pregnancies. There was no significant difference in PTB between SCS and any of the other groups. Concerning the average birth weight we found no significant difference between singletons born after natural conception and SCS. However, a significant difference in average birth weight was found between SCS singletons and singletons born after IVF, ICSI and hormonal treatment, with a significantly higher birth weight in the SCS group. This difference was also observed in the proportion of babies weighing less than 2500 g, with significantly more LBW babies in the IVF and ICSI group compared to the SCS newborns.

INTERPRETATION

Taking into account the small series, PTB and LBW rates in SCS singletons were found to be comparable with singletons born after natural conception. Compared to babies born after ovarian stimulation and IVF/ICSI, SCS singletons had a lower PTB and LBW rates, although the differences were not significant for PTB. Our results confirm previous reports on reassuring perinatal outcomes after using the SCS technology.

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.

Promising Perinatal Outcome after Using a Simplified Low-Cost IVF Culture System Specifically Designed for Resource-Poor Countries

Background: Assisted reproductive techniques services are often not accessible to the majority of infertile couples in Low and Middle Income Countries (LMIC) due to high costs. Lowering IVF laboratory costs is a crucial step to make IVF affordable for a larger part of the world population. We developed a simplified culture system (SCS) which has proven to be effective, and the next step is to prove its safety.Methods: Preterm birth (PTB) and low birthweight (LBW) of 176 singletons born after using the SCS, 105 after fresh embryo transfer (fresh ET), and 71 after frozen embryo transfer (frozen ET) were compared with all IVF/ICSI singletons born in Belgium between 2013 and 2018. When comparing our 105 SCS babies born after fresh ET with all Belgian babies born after conventional IVF only, we also adjusted for 7 risk factors known to influence perinatal outcome, namelythe mother’s age, day of transfer, pituitary inhibition protocol, rank of cycles, number of oocytes retrieved, number of embryos transferred, and gender of the baby.Findings: Before adjustment, we found a significantly higher PTB (10.2% vs. 3.8%, OR 2.852, 95% CI [1.042–7.803], p-value 0.0413) and LBW (9.8% vs. 2.9%, OR 3.692, 95% CI [1.163–11.721], p-value 0.0267) in the conventional IVF group versus SCS after fresh ET. After adjusting for seven risk parameters, these differences remained significant (PTB: OR 2.627, 95% CI [1.013–6.816], p-value 0.0471) and LBW: OR 3.267, 95% CI [1.118–9.549], p-value 0.0305). PTB and LBW between both groups was not significantly different for singletons born after frozen ET. Interpretation: Taking into account the small series, PTB and LBW rates in SCS singletons in FRET cycles are very reassuring and significantly lower compared to babies born after conventional IVF in Belgium. Being aware of its effectiveness, our results offer a good perspective for SCS to become an important tool to implement low-cost IVF in LMIC.

Anthropometric measurements of term singletons at 6 years of age born from fresh and frozen embryo transfer: A multicenter prospective study in Japan

Purpose

The purpose of this study is to compare anthropometric measurements between term singletons conceived via fresh embryo transfer (FreET) and frozen embryo transfer (FET) and those born via natural conception (NC) or fertility treatments milder than assisted reproductive technology (non-ART) at 6 years of age.

Methods

A total of 8149 children were enrolled, and questionnaires about anthropometric measures (weight, height, BMI) were addressed to parents, when the children were 1.5, 3, and 6 years of age. A total of 3299 term singletons were enrolled at birth: 533, 476, 916, and 1374 in the NC, non-ART, FreET, and FET groups, respectively.

Results

A total of 1635 term singletons (290, 176, 467, and 702 in the NC, non-ART, FreET, and FET groups respectively) were enrolled until 6 years of age (follow-up rate, approximately 50%). When non-ART group was used as control, the FreET children were 1.0 cm taller than the non-ART children at 6 years of age, after adjusting for confounding factors. However, no differences were observed in the anthropometric data among the non-ART, ART, and NC children at 6 years of age.

Conclusion

At 6 years of age, term singletons were taller in the FreET group than in the non-ART group, after adjusting for confounders.

Assisted reproductive technology and association with childhood cancer subtypes

OBJECTIVES

To investigate the association between assisted reproductive technology (ART) use and childhood cancer subtype.

STUDY DESIGN

We deployed a cross-sectional survey of 1701 parents of children with cancer about their ART use, demographics, and gestational and perinatal factors. Multivariable logistic regression modeled the association between ART use, birthweight and multiple gestation status with childhood cancer, by subtype.

RESULTS

ART use was highest among children with osteosarcoma relative to children with other cancer types, and this association was statistically significant in multivariable models (OR = 4.4; 95% CI = 1.7-11.3; p = 0.0020). ART use was also elevated among children with hepatoblastoma, but this relationship appeared to be due to the strong associations between ART use and lower birthweight in our sample. No specific ART modality appeared to drive these associations. In univariate models, multiple gestation was associated with a 2.7-fold increased odds of hepatoblastoma (OR = 2.71; 95% CI = 1.14-6.42; p = 0.02) and a 1.6-fold increased odds of neuroblastoma (OR = 1.62; 95% CI = 1.03-2.54; p = 0.03), but these associations were not retained in multivariable models.

CONCLUSIONS

Associations between ART use and hepatoblastoma risk may be attributable to birthweight, a known hepatoblastoma risk factor. ART use may also be associated with osteosarcoma, independent of birthweight, an association not previously observed in studies limited to cancers diagnosed before adolescence. Evaluating long-term health outcomes in children conceived by ART, throughout adolescence and potentially into adulthood, appears warranted.

The cost of preterm birth and cesarean section as a result of infertility and its treatment: A review

Infertility, irrespective of receipt of fertility treatment, is associated with an increased risk of adverse pregnancy outcomes, including cesarean section (CS) and preterm birth (PTB). These complications are associated with significant physical, mental, emotional, social, and financial costs to individuals, healthcare systems, and society at large. Although multiple pregnancy is one of the most significant contributors to the elevated CS and PTB rates in women receiving fertility treatment, singleton pregnancy is also at an increased risk of these outcomes. Single embryo transfer policies through publicly funded in vitro fertilization programs have demonstrated beneficial health outcomes and cost savings. Low-dose aspirin prophylaxis may be considered for PTB reduction in patients with infertility. Finally, upstream prevention strategies such as lifestyle modification and social policies to address the underlying needs for fertility treatment may also beneficially impact both CS and PTB rates.

The gestational age-specific difference in birthweight between singletons born after fresh and frozen embryo transfer: A cohort study

INTRODUCTION

Accumulating studies have suggested singletons born after frozen embryo transfer (FET) were higher than those born after fresh embryo transfer (Fre-ET). However, fewer studies had investigated the gestational age-specific between-group difference in birthweight. This study aimed to investigate the gestational week-specific difference in singleton birthweight after FET vs Fre-ET and explore potential factors that impact the difference.

MATERIAL AND METHODS

In this retrospective cohort study, a total of 25 863 singletons were included. Multivariable linear regression and logistic regression were used to evaluate the between-group differences in mean birthweight and the incidences of large for gestational age (LGA) and small for gestational age (SGA), respectively.

RESULTS

Multivariable regression analyses showed a statistically significant interaction between types of embryo transfer (ie FET vs Fre-ET) and the gestational week on mean birthweight (P < 0.001) and on the risks of large for gestational age (P = 0.001) and small for gestational age (P < 0.001). When stratified by gestational week, the differences in mean birthweight and the risks of LGA and SGA were only observed in singletons born at 37 gestational weeks or later. After adjusting for confounders, full-term but not preterm singletons born after FET had a higher birthweight (3497.58 ± 439.73 g vs 3445.67 ± 450.24 g; adjusted mean difference 58.35 g; 95% confidence interval [CI] 38.72-77.98 g), a higher risk of LGA (24.3% vs 21.1%; adjusted odds ratio [OR] 1.28, 95% CI 1.15-1.42) and a lower risk of SGA (3.1% vs 4.8%; adjusted OR 0.61, 95% CI 0.53-0.70) compared with those born after Fre-ET.

CONCLUSIONS

The differences in birthweight between FET and Fre-ET were observed in full-term singletons but not preterm singletons.

Mode of conception in patients with endometriosis and adverse pregnancy outcomes: a population-based cohort study

OBJECTIVE

To evaluate the association between endometriosis and adverse pregnancy outcomes.

DESIGN

Population-based retrospective cohort study using linked universal health databases through ICES Ontario.

PATIENT(S)

All singleton pregnancies with an estimated date of confinement between October 2006 and February 2014.

INTERVENTION(S)

Endometriosis was determined based on a surgical and/or medical diagnosis (defined as an in-hospital admission or surgery with a diagnosis code of International Classification of Diseases [ICD]9-617 or ICD10-N80 and/or 2 medical consults billed as ICD9-617).

MAIN OUTCOME MEASURE(S)

The association between endometriosis and pregnancy outcomes was quantified by relative risks, derived using modified Poisson regression, and adjusted for maternal age, income quintiles, and history of fibroids (aRR). Mediation analysis was conducted to estimate direct effects of endometriosis diagnosis and indirect effects through mode of conception, namely: infertility without fertility treatment (known infertility but conceived without assistance), ovulation induction or intrauterine insemination, and in vitro fertilization or intracytoplasmic sperm injection, relative to unassisted conception.

RESULT(S)

A total of 19,099 pregnancies had an antecedent diagnosis of endometriosis, while 768,350 did not. Mean time (standard deviation) from endometriosis diagnosis to the index pregnancy was 5.6 (4.3) years. Endometriosis was associated with an increased risk of hypertensive disorders of pregnancy (aRR, 1.09; 95% confidence interval [CI], 1.02-1.16), preterm birth <37 weeks (aRR, 1.26; 95% CI, 1.20-1.33), early preterm birth <34 weeks (aRR, 1.33; 95% CI, 1.17-1.50), placenta previa (aRR, 2.07; 95% CI, 1.84-2.33), placenta abruption (aRR, 1.55; 95% CI, 1.31-1.83), other placental disorders (aRR, 1.77; 95% CI, 1.36-2.30), cesarean delivery (aRR, 1.18; 95% CI, 1.16-1.21), and stillbirth (aRR, 1.32; 95% CI, 1.09-1.59). Mediation analysis suggests that endometriosis directly affects most adverse pregnancy outcomes studied, except for stillbirth where infertility diagnosis or fertility treatment indirectly accounted for part of the increased risk.

CONCLUSION(S)

Endometriosis was associated with adverse pregnancy, independent of infertility diagnosis, or fertility treatment. Future studies should investigate the mechanisms of action and potential interventions.

Mode of conception and risk of spontaneous vs. provider-initiated preterm birth: population-based cohort study

OBJECTIVE

To study the association between mode of conception and risk of preterm birth, including, spontaneous and provider-initiated subtypes.

DESIGN

Population-based retrospective cohort study.

SETTING

Not applicable.

PATIENTS

All singleton livebirths and stillbirth in Ontario, Canada, 2006-2014.

INTERVENTION

The main exposure was mode of conception, namely unassisted conception, infertility without fertility treatment (i.e., known infertility but conceived without assistance), ovulation induction (OI) or intrauterine insemination (IUI), and in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Modified Poisson regression generated risk ratios (RRs) and 95% confidence intervals for the association between exposure categories and preterm birth adjusted for clinically relevant covariates using a propensity score.

MAIN OUTCOME MEASURE(S)

The primary outcome was preterm birth <37 weeks, further categorized as spontaneous or provider-initiated subtypes. The secondary outcome was preterm birth <34 weeks.

RESULTS

We included 732,810 singleton births born to 649,918 mothers, of which 646,926 (88.3%) were from an unassisted conception, 68,822 (9.4%) with infertility but no fertility treatment, 9,024 (1.2%) following OI/IUI, and 8,038 (1.1%) following IVF/ICSI. Preterm birth <37 weeks occurred among 6.0% of births by unassisted conception, 7.7% with infertility without fertility treatment, 8.0% with OI/IUI, and 10.8% following IVF/ICSI. Relative to unassisted conception, the unadjusted RR of provider-initiated preterm birth was 1.30 (1.26-1.33) in women with infertility without fertility treatment, 1.36 (1.26-1.45) after OI/IUI, and 1.82 (1.70-1.93) after IVF/ICSI. The corresponding adjusted RRs (aRR) were 1.23 (1.16-1.31), 1.48 (1.29-1.69), and 2.35 (2.09-2.64). The unadjusted RR of spontaneous preterm birth was 1.22 (1.18-1.27) in women with infertility without fertility treatment, 1.22 (1.12-1.34) after OI/IUI, and 1.47 (1.35-1.60) after IVF/ICSI. The corresponding aRR were 1.15 (1.10-1.19), 1.19 (1.09-1.31), and 1.40 (1.27-1.53). For preterm birth <34 weeks, the RRs followed a similar pattern as for preterm birth <37 weeks, with the exception of women with infertility without fertility treatment (aRR 1.08; confidence interval, 0.95-1.23).

CONCLUSIONS

Infertility and receipt of fertility treatment are each associated with a higher risk of preterm birth, spontaneous and provider-initiated subtypes, even in singleton pregnancies. Strategies are needed to reduce the risk for preterm birth in these women.

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.

Neonatal Outcomes and Long-Term Follow-Up of Children Born from Frozen Embryo, a Narrative Review of Latest Research Findings

In recent years, the growing use of ART (assisted reproductive techniques) has led to a progressive improvement of protocols; embryo freezing is certainly one of the most important innovations. This technique is selectively offered as a tailored approach to reduce the incidence of multiple pregnancies and, most importantly, to lower the risk of developing ovarian hyperstimulation syndrome when used in conjunction with an ovulation-triggering GnRH antagonist. The increase in transfer cycles with frozen embryos made it possible to study the effects of the technique in children thus conceived. Particularly noteworthy is the increase in macrosomal and LGA (large for gestational age) newborns, in addition to a decrease in SGA (small for gestational age) and LBW (low birth weight) newborns. The authors aimed to outline a broad-ranging narrative review by summarizing and elaborating on the most important evidence regarding the neonatal outcome of children born from frozen embryos and provide information on the medium and long-term follow- up of these children. However, given the relatively recent large-scale implementation of such techniques, further studies are needed to provide more conclusive evidence on outcomes and implications.

Early childhood respiratory tract infections according to parental subfertility and conception by assisted reproductive technologies

STUDY QUESTION

Are children conceived by ART or born to subfertile parents more susceptible to upper or lower respiratory tract infections (URTI, LRTI)?

SUMMARY ANSWER

ART-conceived children had a higher frequency of and risk of hospitalization for respiratory infections up to age 3, which was only partly explained by parental subfertility.

WHAT IS KNOWN ALREADY

Some studies report increased risks of infections in children conceived by ART. Results for URTIs and LRTIs are inconclusive, and the contribution of underlying parental subfertility remains unclear.

STUDY DESIGN, SIZE, DURATION

We included 84 102 singletons of the Norwegian Mother, Father and Child Cohort Study (MoBa) born between 1999 and 2009. Mothers reported time-to-pregnancy at recruitment and child history of, frequency of and hospitalization for, respiratory infections when the child was 6, 18 and 36 months old by questionnaires. Subfertility was defined as having taken 12 or more months to conceive. The Medical Birth Registry of Norway (MBRN) provided information on ART. URTI included throat and ear infections, while LRTI included bronchitis, bronchiolitis, respiratory syncytial virus and pneumonia.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used log-binomial regression to estimate risk ratios (RR) and 95% CI of any respiratory tract infection and hospitalization, and negative-binomial regression to calculate incidence rate ratios (IRR) and 95% CI for number of infections. We compared children conceived by ART, and naturally conceived children of subfertile parents, to children of fertile parents (<12 months to conceive) while adjusting for maternal age, education, BMI and smoking during pregnancy and previous livebirths. We accounted for dependency between children born to the same mother.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 7334 (8.7%) singletons were naturally conceived by subfertile parents and 1901 (2.3%) were conceived by ART. Between age 0 and 36 months, 41 609 (49.5%) of children experienced any URTI, 15 542 (18.5%) any LRTI and 4134 (4.9%) were hospitalized due to LRTI. Up to age 3, children conceived by ART had higher frequencies of URTI (adjusted IRR (aIRR) 1.16; 95% CI 1.05–1.28) and hospitalizations due to LRTI (adjusted RR (aRR) 1.25; 95% CI 1.02–1.53), which was not seen for children of subfertile parents. Children conceived by ART were not at higher risks of respiratory infections up to age 18 months; only at age 19–36 months, they had increased risk of any LRTI (aRR 1.16; 95% CI 1.01–1.33), increased frequency of LRTIs (IRR 1.22; 95% CI 1.02–1.47) and a higher risk of hospitalization for LRTI (aRR 1.35; 95% CI 1.01–1.80). They also had an increased frequency of URTIs (aIRR; 1.19; 95% CI 1.07–1.33). Children of subfertile parents only had a higher risk of LRTIs (aRR 1.09; 95% CI 1.01–1.17) at age 19–36 months.

LIMITATIONS, REASONS FOR CAUTION

Self-reported time-to-pregnancy and respiratory tract infections by parents could lead to misclassification. Both the initial participation rate and loss to follow up in the MoBa limits generalizability to the general Norwegian population.

WIDER IMPLICATIONS OF THE FINDINGS

ART-conceived children might be more susceptible to respiratory tract infections in early childhood. This appears to be only partly explained by underlying parental subfertility. Exactly what aspects related to the ART procedure might be reflected in these associations need to be further investigated.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was received from the Swiss National Science Foundation (P2BEP3_191798), the Research Council of Norway (no. 262700), and the European Research Council (no. 947684). All authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Comparison of pregnancy and live birth rates between fresh day 5 morula transfer and fresh day 6 blastocyst transfer following extended culture for slow growing embryos

PURPOSE

The aim of this study is to evaluate and compare the outcomes of fresh day 5 morula transfers and fresh day 6 blastocyst transfers after extended culture, in women with a whole cohort of slow growing embryos.

METHODS

Fresh embryo transfer cycles of patients that underwent intracytoplasmic sperm injection between 2013 and 2020 with a whole cohort of slow developing embryos on 5th day of fertilization were evaluated for this retrospective cohort study. Outcomes of day 5 morula transfers and day 6 blastocyst transfers after extended culture were compared.

RESULTS

Out of 479 patients, day 5 morula transfers were performed to 194 and embryo culturing was extended to day 6 in 285 women. Blastocyst formation was observed in 129 of 285 patients in extended culture group. Implantation rate of day 6 blastocyst transfer group was significantly higher than day 5 morula transfer group (27% vs. 12%, p < 0.001). However, clinical pregnancy (17% vs 15.4%) and live birth rates (14.4% vs 13%) were found similar in day 5 morula transfer and extended culture group per initiated cycle.

CONCLUSION

Although implantation capacity of day 6 blastocysts seems higher comparing to day 5 morulas, clinical pregnancy and live birth rates are similar among intention to treat population in fresh day 5 morula transfers and day 6 blastocyst transfers after extended culture for women that cohorts consist of only slow developing embryos.

Attention-deficit hyperactivity disorder in children born to mothers with infertility: a population-based cohort study

STUDY QUESTION

Is the risk of attention-deficit hyperactivity disorder (ADHD) increased in children born to mothers with infertility, or after receipt of fertility treatment, compared to mothers with unassisted conception?

SUMMARY ANSWER

Infertility itself may be associated with ADHD in the offspring, which is not amplified by the use of fertility treatment.

WHAT IS KNOWN ALREADY

Infertility, and use of fertility treatment, is common. The long-term neurodevelopmental outcome of a child born to a mother with infertility, including the risk of ADHD, remains unclear.

STUDY DESIGN, SIZE, DURATION

This population-based cohort study comprised all singleton and multiple hospital births in Ontario, Canada, 2006–2014. Outcomes were assessed up to June 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Linked administrative datasets were used to capture all hospital births in Ontario, maternal health and pregnancy measures, fertility treatment and child outcomes. Included were all children born at ≥24 weeks gestation between 2006 and 2014, and who were alive at age 4 years. The main exposure was mode of conception, namely (i) unassisted conception (reference group), (ii) infertility without fertility treatment (history of an infertility consultation with a physician within 2 years prior to conception but no fertility treatment), (iii) ovulation induction (OI) or intrauterine insemination (IUI) and (iv) IVF or intracytoplasmic sperm injection (ICSI). The main outcome was a diagnosis of ADHD after age 4 years and assessed up to June 2020. Hazard ratios (HRs) were adjusted for maternal age, income quintile, rurality, immigration status, smoking, obesity, parity, any drug or alcohol use, maternal history of mental illness including ADHD, pre-pregnancy diabetes mellitus or chronic hypertension and infant sex. In addition, we performed pre-planned stratified analyses by mode of delivery (vaginal or caesarean delivery), infant sex, multiplicity (singleton or multiple), timing of birth (term or preterm <37 weeks) and neonatal adverse morbidity (absent or present).

MAIN RESULTS AND THE ROLE OF CHANCE

The study included 925 488 children born to 663 144 mothers, of whom 805 748 (87%) were from an unassisted conception, 94 206 (10.2%) followed infertility but no fertility treatment, 11 777 (1.3%) followed OI/IUI and 13 757 (1.5%) followed IVF/ICSI. Starting at age 4 years, children were followed for a median (interquartile range) of 6 (4–8) years. ADHD occurred among 7.0% of offspring in the unassisted conception group, 7.5% in the infertility without fertility treatment group, 6.8% in the OI/IUI group and 6.3% in the IVF/ICSI group. The incidence rate (per 1000 person-years) of ADHD was 12.0 among children in the unassisted conception group, 12.8 in the infertility without fertility treatment group, 12.9 in the OI/IUI group and 12.2 in the IVF/ICSI group. Relative to the unassisted conception group, the adjusted HR for ADHD was 1.19 (95% CI 1.16–1.22) in the infertility without fertility treatment group, 1.09 (95% CI 1.01–1.17) in the OI/IUI group and 1.12 (95% CI 1.04–1.20) in the IVF/ICSI group. In the stratified analyses, these patterns of risk for ADHD were largely preserved. An exception was seen in the sex-stratified analyses, wherein females had lower absolute rates of ADHD but relatively higher HRs compared with that seen among males.

LIMITATIONS, REASONS FOR CAUTION

Some mothers in the isolated infertility group may have received undocumented OI oral therapy, thereby leading to possible misclassification of their exposure status. Parenting behaviour, schooling and paternal mental health measures were not known, leading to potential residual confounding.

WIDER IMPLICATIONS OF THE FINDINGS

Infertility, even without treatment, is a modest risk factor for the development of ADHD in childhood. The reason underlying this finding warrants further study.

STUDY FUNDING/COMPETING INTEREST(s)

This study was made possible with funding from the Canadian Institutes of Health Research, Grant number PJT 165840. The authors report no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

DNA methylation in newborns conceived by assisted reproductive technology

Assisted reproductive technology (ART) may affect fetal development through epigenetic mechanisms as the timing of ART procedures coincides with the extensive epigenetic remodeling occurring between fertilization and embryo implantation. However, it is unknown to what extent ART procedures alter the fetal epigenome. Underlying parental characteristics and subfertility may also play a role. Here we identify differences in cord blood DNA methylation, measured using the Illumina EPIC platform, between 962 ART conceived and 983 naturally conceived singleton newborns. We show that ART conceived newborns display widespread differences in DNA methylation, and overall less methylation across the genome. There were 607 genome-wide differentially methylated CpGs. We find differences in 176 known genes, including genes related to growth, neurodevelopment, and other health outcomes that have been associated with ART. Both fresh and frozen embryo transfer show DNA methylation differences. Associations persist after controlling for parents’ DNA methylation, and are not explained by parental subfertility.

Timing of assisted reproduction technology (ART) procedures coincides with extensive epigenetic remodeling early after conception. Here the authors identify 176 DNA methylation differences in cord blood of newborns conceived with ART. including genes related to growth, neurodevelopment, and cancer.

The effects of post-frozen-thawed embryo transfer pregnancy on early fetal development

AIM

Frozen-thawed embryo transfer (FET) has gained popularity as an assistive reproductive technology despite its increased risk of large-for-gestational-age offspring. This study aimed to analyze the effect of FET on fetal development, particularly the growth rate and estimated fetal weight (EFW) throughout pregnancy.

METHODS

This was a single-center, retrospective study that examined 97 patients with FET conception and 477 patients with natural conception (NC) who underwent labor and delivery at our clinic between December 2015 and June 2019. Crown-rump length (CRL) in the first trimester and EFW measurements in the second and third trimesters were obtained from transabdominal ultrasound records. Birthweight was adjusted for sex, parity, and gestational age. Regression coefficients of CRL, EFW, and birthweight were compared between the FET and NC groups to examine the growth rate. Multiple regression analysis was performed to determine the relationship between birth size and baseline characteristics.

RESULTS

The growth rate was higher in the first trimester in the FET group than in the NC group (difference: 0.19 mm/day, p = 0.018). CRL, EFW, and adjusted birthweight were higher in the FET group than in the NC group throughout pregnancy. The factors associated with the development of larger offspring through FET than through NC were advanced maternal age, primiparity, cesarean section delivery, and high birthweight.

CONCLUSIONS

Throughout pregnancy, FET resulted in a larger offspring than in NC, with accelerated growth observed only during the first trimester. Thus, FET highly affects early fetal development.

Caesarean birth in women with infertility: population-based cohort study

Objective

Caesarean section (CS) is more common following infertility treatment (IT) but the reasons why remain unclear and confounded. The Robson 10‐Group Classification System (TGCS) may further explain variation in CS rates. We assessed the association between mode of conception and CS across Robson groups.

Design

Population‐based cohort study.

Setting

Ontario, Canada, in a public healthcare system.

Population

921 023 births, 2006–2014.

Methods

Modified Poisson regression produced relative risks (RR) and 95% confidence intervals, comparing the risk of CS among women with (1) subfertility without IT, (2) non‐invasive IT (OI, IUI) or (3) invasive IT (IVF)—each relative to (4) spontaneous conception (SC).

Main outcome measures

CS rate according to one of four modes of conception, overall and stratified by each of the TGCS groups.

Results

Relative to SC (26.9%), the risk of CS increased in those with subfertility without IT (RR 1.17, 95% CI 1.16–1.18), non‐invasive IT (RR 1.21, 95% CI 1.18–1.24) and invasive IT (RR 1.39, 95% CI 1.36–1.42). Within each Robson group, similar patterns of RRs were seen, but with markedly differing rates. For example, in Group 1 (nulliparous, singleton, cephalic at ≥37 weeks, with spontaneous labour), the respective rates were 15.0, 19.4, 18.7 and 21.9%; in Group 2 (nulliparous, singleton, cephalic at ≥37 weeks, without spontaneous labour), the rates were 35.9, 44.4, 43.2 and 54.1%; and in Group 8 (multiple pregnancy), they were 55.9, 67.5, 65.0 and 69.3%, respectively.

Conclusions

CS is relatively more common in women with subfertility and those receiving IT, an effect that persists across Robson groups.

Tweetable abstract

Caesarean delivery is more common in women with infertility independent of demographics and prenatal conditions.

Caesarean delivery is more common in women with infertility independent of demographics and prenatal conditions.

Do frozen embryo transfers modify the epigenetic control of imprinted genes and transposable elements in newborns compared with fresh embryo transfers and natural conceptions?

OBJECTIVE

To determine whether the epigenetic control of imprinted genes (IGs) and transposable elements (TEs) differs at birth between fresh or frozen embryo transfers and natural conceptions.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENT(S)

A total of 202 singleton births were divided into three groups: 84 natural pregnancies (controls), 66 in vitro fertilization/intracytoplasmic sperm injection with fresh embryo transfers, and 52 vitro fertilization/intracytoplasmic sperm injection with frozen embryo transfers.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pyrosequencing was used to assess the DNA methylation profiles of three IGs (H19/IGF2:IG-DMR [two sequences], KCNQ1OT1:TSS-DMR, and SNURF:TSS-DMR) and two TEs (LINE-1 and HERV-FRD) in cord blood and placenta. The quantitative reverse transcriptase polymerase chain reaction was used to study the transcription of three IGs (H19, KCNQ1, and SNRPN) and two TEs (LINE-1 and ORF2).

RESULT(S)

After adjustment, the placental DNA methylation levels of H19/IGF2 were lower in the fresh embryo transfer group than in the control (H19/IGF2-seq1) and frozen embryo transfer (H19/IGF2-seq2) groups. The DNA methylation rate for LINE-1 was lower in placentas from the fresh embryo transfer group than in placentas from the control and frozen embryo transfer groups and for HERV-FRD compared with controls. In cord blood, DNA methylation levels were not significantly associated with the mode of conception. The relative expression of LINE-1 and ORF2 was decreased in both cord blood and placental tissues from fresh embryo transfer conceptions compared with natural conceptions and frozen embryo transfer conceptions.

CONCLUSION(S)

Compared with natural conceptions and frozen embryo transfers, fresh embryo transfers were associated with methylation and/or transcription changes in some TEs and IGs, mostly in placental samples, which could indicate altered placental epigenetic regulation resulting from ovarian stimulation protocols.

Absolute Risk of Adverse Obstetric Outcomes Among Twin Pregnancies After In Vitro Fertilization by Maternal Age

IMPORTANCE

Twin pregnancy is a common occurrence in pregnancies conceived with in vitro fertilization (IVF), but the absolute risk of adverse obstetric outcomes stratified by IVF, twin or singleton pregnancy, and maternal age are unknown.

OBJECTIVE

To estimate the absolute risk of adverse obstetric outcomes at each maternal age among twin pregnancies conceived with IVF.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study included pregnant women with infants born from January 1, 2013, to December 31, 2018, based on the Hospital Quality Monitoring System in China. Data were analyzed from September 1, 2020, to June 30, 2021.

EXPOSURES

Twin pregnancy with IVF (IVF-T), singleton pregnancy with IVF (IVF-S), twin pregnancy with non-IVF (nIVF-T), and singleton pregnancy with non-IVF (nIVF-S).

MAIN OUTCOMES AND MEASURES

Sixteen obstetric outcomes, including 10 maternal complications (gestational hypertension, eclampsia and preeclampsia, gestational diabetes, placenta previa, placental abruption, placenta accreta, preterm birth, dystocia, cesarean delivery, and postpartum hemorrhage) and 6 neonatal complications (fetal growth restriction, low birth weight, very low birth weight, macrosomia, malformation, and stillbirth).

RESULTS

Among 16 879 728 pregnant women aged 20 to 49 years (mean [SD] age, 29.2 [4.7] years), the twin-pregnancy rates were 32.1% in the IVF group and 1.5% in the non-IVF group (relative risk, 20.8; 95% CI, 20.6-20.9). The most common adverse obstetric outcomes after pregnancy conceived with IVF were cesarean delivery (88.8%), low birth weight (43.8%), preterm birth (39.6%), gestational diabetes (20.5%), gestational hypertension and preeclampsia and eclampsia (17.5%), dystocia (16.8%), and postpartum hemorrhage (11.9%). The absolute risk of most adverse obstetric outcomes in each subgroup presented in 2 dominant patterns: Pattern A indicated the absolute risk ranging from IVF-T to nIVF-T to IVF-S to nIVF-S, and pattern B indicated the absolute risk ranging from IVF-T to IVF-S to nIVF-T to nIVF-S. Both patterns showed an elevated obstetric risk with increasing maternal age in each subgroup.

CONCLUSIONS AND RELEVANCE

In this cohort study, twin pregnancy, IVF, and advanced maternal age were independently associated with adverse obstetric outcomes. Given these findings, promotion of the elective single embryo transfer strategy is needed to reduce multiple pregnancies following IVF technologies. Unnecessary cesarean delivery shouldh be avoided in all pregnant women.

Association of medically assisted reproduction with offspring cord blood DNA methylation across cohorts

STUDY QUESTION

Is cord blood DNA methylation associated with having been conceived by medically assisted reproduction?

SUMMARY ANSWER

This study does not provide strong evidence of an association of conception by medically assisted reproduction with variation in infant blood cell DNA methylation.

WHAT IS KNOWN ALREADY

Medically assisted reproduction consists of procedures used to help infertile/subfertile couples conceive, including ART. Due to its importance in gene regulation during early development programming, DNA methylation and its perturbations associated with medically assisted reproduction could reveal new insights into the biological effects of assisted reproductive technologies and potential adverse offspring outcomes.

STUDY DESIGN, SIZE, DURATION

We investigated the association of DNA methylation and medically assisted reproduction using a case–control study design (N = 205 medically assisted reproduction cases and N = 2439 naturally conceived controls in discovery cohorts; N = 149 ART cases and N = 58 non-ART controls in replication cohort).

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

We assessed the association between medically assisted reproduction and DNA methylation at birth in cord blood (205 medically assisted conceptions and 2439 naturally conceived controls) at >450 000 CpG sites across the genome in two sub-samples of the UK Avon Longitudinal Study of Parents and Children (ALSPAC) and two sub-samples of the Norwegian Mother, Father and Child Cohort Study (MoBa) by meta-analysis. We explored replication of findings in the Australian Clinical review of the Health of adults conceived following Assisted Reproductive Technologies (CHART) study (N = 149 ART conceptions and N = 58 controls).

MAIN RESULTS AND THE ROLE OF CHANCE

The ALSPAC and MoBa meta-analysis revealed evidence of association between conception by medically assisted reproduction and DNA methylation (false-discovery-rate-corrected P-value < 0.05) at five CpG sites which are annotated to two genes (percentage difference in methylation per CpG, cg24051276: Beta = 0.23 (95% CI 0.15,0.31); cg00012522: Beta = 0.47 (95% CI 0.31, 0.63); cg17855264: Beta = 0.31 (95% CI 0.20, 0.43); cg17132421: Beta = 0.30 (95% CI 0.18, 0.42); cg18529845: Beta = 0.41 (95% CI 0.25, 0.57)). Methylation at three of these sites has been previously linked to cancer, aging, HIV infection and neurological diseases. None of these associations replicated in the CHART cohort. There was evidence of a functional role of medically assisted reproduction-induced hypermethylation at CpG sites located within regulatory regions as shown by putative transcription factor binding and chromatin remodelling.

LIMITATIONS, REASONS FOR CAUTIONS

While insufficient power is likely, heterogeneity in types of medically assisted reproduction procedures and between populations may also contribute. Larger studies might identify replicable variation in DNA methylation at birth due to medically assisted reproduction.

WIDER IMPLICATIONS OF THE FINDINGS

Newborns conceived with medically assisted procedures present with divergent DNA methylation in cord blood white cells. If these associations are true and causal, they might have long-term consequences for offspring health.

STUDY FUNDING/COMPETING INTERESTS(S)

This study has been supported by the US National Institute of Health (R01 DK10324), the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no. 669545, European Union’s Horizon 2020 research and innovation programme under Grant agreement no. 733206 (LifeCycle) and the NIHR Biomedical Centre at the University Hospitals Bristol NHS Foundation Trust and the University of Bristol. The UK Medical Research Council and Wellcome (Grant ref: 102215/2/13/2) and the University of Bristol provide core support for ALSPAC. Methylation data in the ALSPAC cohort were generated as part of the UK BBSRC funded (BB/I025751/1 and BB/I025263/1) Accessible Resource for Integrated Epigenomic Studies (ARIES, http://www.ariesepigenomics.org.uk). D.C., J.J., C.L.R. D.A.L and H.R.E. work in a Unit that is supported by the University of Bristol and the UK Medical Research Council (Grant nos. MC_UU_00011/1, MC_UU_00011/5 and MC_UU_00011/6). B.N. is supported by an NHMRC (Australia) Investigator Grant (1173314). ALSPAC GWAS data were generated by Sample Logistics and Genotyping Facilities at Wellcome Sanger Institute and LabCorp (Laboratory Corporation of America) using support from 23andMe. The Norwegian Mother, Father and Child Cohort Study is supported by the Norwegian Ministry of Health and Care Services and the Ministry of Education and Research, NIH/NIEHS (Contract no. N01-ES-75558), NIH/NINDS (Grant nos. (i) UO1 NS 047537-01 and (ii) UO1 NS 047537-06A1). For this work, MoBa 1 and 2 were supported by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences (Z01-ES-49019) and the Norwegian Research Council/BIOBANK (Grant no. 221097). This work was partly supported by the Research Council of Norway through its Centres of Excellence funding scheme, Project no. 262700.

D.A.L. has received support from national and international government and charity funders, as well as from Roche Diagnostics and Medtronic for research unrelated to this study. The other authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Cohort profile: a national, population-based cohort of children born after assisted conception in the UK (1992-2009): methodology and birthweight analysis

PURPOSE

To generate a large cohort of children born after assisted reproductive technology (ART) in the UK between 1992 and 2009, their naturally conceived siblings (NCS) and matched naturally conceived population (NCP) controls and linking this with health outcome data to allow exploration of the effects of ART. The effects of fresh and frozen embryo transfer on birth weight (BW) were analysed to test the validity of the cohort.

PARTICIPANTS

Children recorded on the Human Fertilisation and Embryology Authority (HFEA) register as being born after ART between 1992 and 2009, their NCS and matched NCP controls linked to Office for National Statistics birth registration dataset (HFEA-ONS cohort). This cohort was further linked to the UK Hospital Episode Statistics database to allow monitoring of the child's post-natal health outcomes up to 2015 (HFEA-ONS-HES subcohort).

FINDINGS TO DATE

The HFEA-ONS cohort consisted of 75 348 children born after non-donor ART carried out in the UK between 1 April 1992 and 31 July 2009 and successfully linked to birth registration records, 14 763 NCS and 164 823 matched NCP controls. The HFEA-ONS-HES subcohort included 63 877 ART, 11 343 NCS and 127 544 matched NCP controls further linked to health outcome data. The exemplar analysis showed that children born after fresh embryo transfers were lighter (BW difference: -131 g, 95% CI: -140 to -123) and those born after frozen embryo transfers were heavier (BW difference: 35 g, 95% CI: 19 to 52) than the NCP controls. The within-sibling analyses were directionally consistent with the population control analyses, but attenuated markedly for the fresh versus natural conception (BW difference: -54 g; 95% CI: -72 to -36) and increased markedly for the frozen versus natural conception (BW difference: 152 g; 95% CI: 113 to 190) analyses.

FUTURE PLANS

To use this cohort to explore the relationship between ART conception and short-term and long-term health outcomes in offspring.

Preparation of the Endometrium for Frozen Embryo Transfer: A Systematic Review

Despite the worldwide increase in frozen embryo transfer, the search for the best protocol to prime endometrium continues. Well-designed trials comparing various frozen embryo transfer protocols in terms of live birth rates, maternal, obstetric and neonatal outcome are urgently required. Currently, low-quality evidence indicates that, natural cycle, either true natural cycle or modified natural cycle, is superior to hormone replacement treatment protocol. Regarding warmed blastocyst transfer and frozen embryo transfer timing, the evidence suggests the 6th day of progesterone start, LH surge+6 day and hCG+7 day in hormone replacement treatment, true natural cycle and modified natural cycle protocols, respectively. Time corrections, due to inter-personal differences in the window of implantation or day of vitrification (day 5 or 6), should be explored further. Recently available evidence clearly indicates that, in hormone replacement treatment and natural cycles, there might be marked inter-personal variation in serum progesterone levels with an impact on reproductive outcomes, despite the use of the same dose and route of progesterone administration. The place of progesterone rescue protocols in patients with low serum progesterone levels one day prior to warmed blastocyst transfer in hormone replacement treatment and natural cycles is likely to be intensively explored in near future.

Assisted reproductive technology and hypertensive disorders of pregnancy: systematic review and meta-analyses

Background

Hypertensive disorders of pregnancy (HDP) is one of the most common pregnancy complications and causes of maternal morbidity and mortality. Assisted reproductive technology (ART) has been associated with adverse pregnancy outcomes, including HDP. However, the impact of multiple pregnancies, oocyte donation, as well as fresh and frozen embryo transfer needs to be further studied. We conducted a systematic review and meta-analyses to evaluate the association between ART and HDP or preeclampsia relative to spontaneous conception (SC).

Methods

We identified studies from EMBASE, MEDLINE, and Cochrane Library (up to April 8, 2020) and manually using structured search strategies. Cohort studies that included pregnancies after in vitro fertilization (IVF) with or without intracytoplasmic sperm fertilization (ICSI) relative to SC with HDP or preeclampsia as the outcome of interest were included. The control group was women who conceived spontaneously without ART or fertility medications. The pooled results were reported in odds ratios (OR) with 95% confidence intervals based on random effects models. Numbers needed to harm (NNH) were calculated based on absolute risk differences between exposure and control groups.

Results

Eighty-five studies were included after a screening of 1879 abstracts and 283 full text articles. Compared to SC, IVF/ICSI singleton pregnancies (OR 1.70; 95% CI 1.60–1.80; I² = 80%) and multiple pregnancies (OR 1.34; 95% CI 1.20–1.50; I² = 76%) were both associated with higher odds of HDP. Singleton pregnancies with oocyte donation had the highest odds of HDP out of all groups analyzed (OR 4.42; 95% CI 3.00–6.51; I² = 83%). Frozen embryo transfer resulted in higher odds of HDP (OR 1.74; 95% CI 1.58–1.92; I² = 55%) than fresh embryo transfer (OR 1.43; 95% CI 1.33–1.53; I² = 72%). The associations between IVF/ICSI pregnancies and SC were similar for preeclampsia. Most interventions had an NNH of 40 to 100, while singleton and multiple oocyte donation pregnancies had particularly low NNH for HDP (16 and 10, respectively).

Conclusions

Our meta-analysis confirmed that IVF/ICSI pregnancies are at higher odds of HDP and preeclampsia than SC, irrespective of the plurality. The odds were especially high in frozen embryo transfer and oocyte donation pregnancies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-03938-8.

Separating parental and treatment contributions to perinatal health after fresh and frozen embryo transfer in assisted reproduction: A cohort study with within-sibship analysis

BACKGROUND

Compared to naturally conceived children, adverse perinatal outcomes are more common among children born after assisted reproductive technology with fresh embryo transfer (fresh-ET) or frozen embryo transfer (frozen-ET). However, most previous studies could not adequately control for family confounding factors such as subfertility. We compared birth size and duration of pregnancy among infants born after fresh-ET or frozen-ET versus natural conception, using a within-sibship design to account for confounding by maternal factors.

METHODS AND FINDINGS

This registry-based cohort study with nationwide data from Denmark (1994-2014), Norway (1988-2015), and Sweden (1988-2015) consisted of 4,510,790 live-born singletons, 4,414,703 from natural conception, 78,095 from fresh-ET, and 17,990 from frozen-ET. We identified 33,056 offspring sibling groups with the same mother, conceived by at least 2 different conception methods. Outcomes were mean birthweight, small and large for gestational age, mean gestational age, preterm (<37 weeks, versus ≥37), and very preterm birth (<32 weeks, versus ≥32). Singletons born after fresh-ET had lower mean birthweight (-51 g, 95% CI -58 to -45, p < 0.001) and increased odds of small for gestational age (odds ratio [OR] 1.20, 95% CI 1.08 to 1.34, p < 0.001), while those born after frozen-ET had higher mean birthweight (82 g, 95% CI 70 to 94, p < 0.001) and increased odds of large for gestational age (OR 1.84, 95% CI 1.56 to 2.17, p < 0.001), compared to naturally conceived siblings. Conventional population analyses gave similar results. Compared to naturally conceived siblings, mean gestational age was lower after fresh-ET (-1.0 days, 95% CI -1.2 to -0.8, p < 0.001), but not after frozen-ET (0.3 days, 95% CI 0.0 to 0.6, p = 0.028). There were increased odds of preterm birth after fresh-ET (OR 1.27, 95% CI 1.17 to 1.37, p < 0.001), and in most models after frozen-ET, versus naturally conceived siblings, with somewhat stronger associations in population analyses. For very preterm birth, population analyses showed increased odds for both fresh-ET (OR 2.03, 95% CI 1.90 to 2.12, p < 0.001) and frozen-ET (OR 1.66, 95% CI 1.42 to 1.94, p < 0.001) compared with natural conception, but results were notably attenuated within siblings (OR 1.18, 95% CI 1.0 to 1.41, p = 0.059, and OR 0.92, 95% CI 0.67 to 1.27, p = 0.6, for fresh-ET and frozen-ET, respectively). Sensitivity analyses in full siblings, in siblings born within 3-year interval, by birth order, and restricting to single embryo transfers and blastocyst transfers were consistent with the main analyses. Main limitations were high proportions of missing data on maternal body mass index and smoking.

CONCLUSIONS

We found that infants conceived by fresh-ET had lower birthweight and increased odds of small for gestational age, and those conceived by frozen-ET had higher birthweight and increased odds of large for gestational age. Conception by either fresh-ET or frozen-ET was associated with increased odds of preterm birth. That these findings were observed within siblings, as well as in conventional multivariable population analyses, reduces the likelihood that they are explained by confounding or selection bias.

TRIAL REGISTRATION

ClinicalTrials.gov ISRCTN11780826.

Caesarean section in pregnancies conceived by assisted reproductive technology: a systematic review and meta-analysis

Background

Caesarean section rates are higher among pregnancies conceived by assisted reproductive technology (ART) compared to spontaneous conceptions (SC), implying an increase in neonatal and maternal morbidity. We aimed to compare caesarean section rates in ART pregnancies versus SC, overall, by indication (elective versus emergent), and by type of ART treatment (in-vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), fresh embryo transfer, frozen embryo transfer) in a systematic review and meta-analysis.

Methods

We searched Medline, EMBASE and CINAHL databases using the OVID Platform from 1993 to 2019, and the search was completed in January 2020. The eligibility criteria were cohort studies with singleton conceptions after in-vitro fertilization and/or intracytoplasmic sperm injection using autologous oocytes versus spontaneous conceptions. The study quality was assessed using the Newcastle Ottawa Scale and GRADE approach. Meta-analyses were performed using odds ratios (OR) with a 95% confidence interval (CI) using random effect models in RevMan 5.3, and I-squared (I²) test > 75% was considered as high heterogeneity.

Results

One thousand seven hundred fifty studies were identified from the search of which 34 met the inclusion criteria. Compared to spontaneous conceptions, IVF/ICSI pregnancies were associated with a 1.90-fold increase of odds of caesarean section (95% CI 1.76, 2.06). When stratified by indication, IVF/ICSI pregnancies were associated with a 1.91-fold increase of odds of elective caesarean section (95% CI 1.37, 2.67) and 1.38-fold increase of odds of emergent caesarean section (95% CI 1.09, 1.75). The heterogeneity of the studies was high and the GRADE assessment moderate to low, which can be explained by the observational design of the included studies.

Conclusions

The odds of delivering by caesarean section are greater for ART singleton pregnancies compared to spontaneous conceptions. Preconception and pregnancy care plans should focus on minimizing the risks that may lead to emergency caesarean sections and finding strategies to understand and decrease the rate of elective caesarean sections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-03711-x.

Obstetric and perinatal outcomes of in vitro fertilization and natural pregnancies in the same mother

OBJECTIVE

To compare obstetric and perinatal outcomes between pregnancies conceived using in vitro fertilization (IVF) and natural pregnancies of the same women.

DESIGN

This was a case-control study of deliveries between November 2008 and January 2020 in which each IVF pregnancy was matched to a natural pregnancy of the same woman (1:1 ratio).

SETTING

University hospital.

PATIENT(S)

We included women with consecutive live singleton deliveries (>24 weeks of gestation) at the Edith Wolfson Medical Center. We excluded IVF pregnancies attained using egg donation.

INTERVENTION(S)

In vitro fertilization-attained pregnancies (as compared with natural ones).

MAIN OUTCOME MEASURE(S)

Primary outcome: preterm birth (PTB).

SECONDARY OUTCOMES

small for gestational age (SGA) neonates and pregnancy-induced hypertension (PIH; gestational hypertension or pre-eclampsia).

RESULT(S)

A total of 544 IVF pregnancies were matched to 544 natural pregnancies, each in the same woman. In 292 women (53.7%), the natural pregnancy preceded the IVF pregnancy. Maternal age was significantly higher in IVF deliveries. Gestational age at delivery and the rates of PTB, PIH, instrumental delivery, cesarean delivery, and SGA neonates were comparable between IVF and natural pregnancies. Birth weight was slightly lower in IVF pregnancies. On multivariate analysis, IVF was not independently associated with PTB, SGA, or PIH after adjustment for confounders.

CONCLUSION(S)

When compared in a cohort of the same women, natural and IVF-attained pregnancies did not differ with regard to obstetric and perinatal outcomes.