Association between peak serum estradiol level during controlled ovarian stimulation and neonatal birthweight in freeze-all cycles: a retrospective study of 8501 singleton live births

The potential toxic effects of estrogen exposure on neural and vascular development in zebrafish

Estrogens and estrogenic chemicals are endocrine-disrupting chemicals (EDCs). The potential toxicity of EDCs to humans and aquatic organisms has become increasingly concerning. However, at present, the potential toxic mechanisms of EDCs on neural and vascular development are still being fully investigated. During the study, we utilized zebrafish to assess the developmental neural and vascular toxicity of different estrogens. The results indicated that zebrafish treated with different estrogens, especially E2, exhibit developmental malformations, including increased mortality, decreased body length, decreased heart rate, aberrant swimming behavior, and increased developmental malformations, including spinal curvature (SC), yolk edema (YE) and pericaidial edema (PE), in a dose-dependent manner with 72 h-treated. Further morphological evaluation revealed that E2 exposure significantly induced motor neural abnormalities in zebrafish embryos. In addition, treated with these three estrogens also impaired the vascular development in the early stage of zebrafish embryos. Mechanistically, the identification of downstream factors revealed that several key neural and vascular development-related genes, including syn2a, gfap, gap43, shha, kdr, flt1 and flt4, were transcriptionally downregulated after estrogen exposure in zebrafish, suggesting that estrogen exposure might cause neural and vascular toxicity by interfering the mRNA levels of genes relevant to neural and vascular development.

Effect of diminished ovarian reserve on the outcome of fresh embryo transfer in IVF/ICSI cycles among young women: A retrospective cohort study

OBJECTIVE

This study aims to investigate the effect of diminished ovarian reserve (DOR) on the clinical outcomes and maternal and infant safety of in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) procedures in young women aged ≤ 35 years.

METHODS

A retrospective cohort study was performed to analyze the clinical data of 4,203 infertile women aged ≤ 35 years who underwent fresh embryo transfer (ET) in IVF/ICSI cycles. The data were collected from their initial visits to Fujian Maternity and Child Health Hospital between January 2015 and January 2022. Based on their ovarian reserve, the participants were categorized into two groups: DOR group (n = 1,027) and non-DOR group (n = 3,176). A propensity score matching (PSM) method was employed to ensure a relatively balanced distribution of covariates. The primary outcome assessed in this study was the live birth rate, while the secondary observation indicators included rates of high-quality embryo development, blastocyst formation, clinical pregnancy, and miscarriage, along with perinatal complications, neonatal birth weight, and the incidence of low birth weight (LBW).

RESULTS

The DOR group showed notably lowered rates of blastocyst formation (59.8% vs. 64.1%), embryo implantation (29.8% vs.33.3%), clinical pregnancy (47.9% vs. 53.6%), and live birth (40.6% vs. 45.7%) compared to the non-DOR group (all P < 0.05). However, no statistically significant differences were observed in the high-quality embryo rate, miscarriage rate, perinatal complications, neonatal birth weight, or LBW incidence in infants between both groups (all P > 0.05).

CONCLUSION

DOR has been found to reduce both clinical pregnancy and live birth rates in young females undergoing fresh ET in IVF/ICSI cycles. However, this reduction does not increase the risk of perinatal complications or LBW of infants through live birth cycles.

Estradiol on trigger day: Irrelevant to live birth rates of fresh cycles but positively associated with cumulative live birth rates

OBJECTIVE

To assess the effects of estradiol (E2) on trigger day on cumulative live birth rates (CLBRs), and pregnancy outcomes after fresh and frozen-thawed embryo transfer (FET).

METHODS

This multicenter retrospective cohort study included 42 315 patients from five reproductive centers. Six subgroups were divided according to E2 on trigger day (<1000, 1000-2000, 2000-3000, 3000-4000, 4000-5000, >5000 pg/mL). Smooth curve fitting and nonlinear mixed-effects models were used.

RESULTS

When E2 was <5500 pg/mL, the CLBR increased by 10% for every 1000 pg/mL increase in E2. When E2 was between 5500 and 13 281 pg/mL, CLBR increased by 1.8% for every 1000 pg/mL increase in E2. When E2 was >13 281 pg/mL, CLBR decreased by 3% for every 1000 pg/mL increase in E2. From group E2 < 1000 to group E2 > 5000 pg/mL, pregnancy and live birth rates in fresh cycles were not related to E2. The live birth rate after FET was higher in the E2 ≥ 5000 pg/mL group than in the E2 < 1000 pg/mL group (odds ratio [OR] 4.03, and 95% confidence interval [CI] 3.74-4.35; adjusted OR 1.20, 95% CI 1.05-1.37).

CONCLUSION

CLBR is associated with E2 on trigger day in a segmented manner. Pregnancy and live birth rates in fresh cycles were not associated with E2. The live birth rate in FET cycles was highest when E2 ≥ 5000 pg/mL.

The duration of estrogen treatment before progesterone application does not affect neonatal and perinatal outcomes in frozen embryo transfer cycles

Objective

To explore whether the duration of estrogen treatment before progesterone application affects neonatal and perinatal outcomes in artificial frozen embryo transfer (FET) cycles.

Methods

This was a retrospective cohort study. Patients who underwent FET via artificial cycles and delivered a singleton live birth between January 2015 and August 2019 were included in the analysis. According to the duration of estrogen treatment before progesterone application, we divided the cycles into four groups: ①≤12 days, ②13-15 days, ③16-19 days, and ④≥20 days. The '≤12 days group' was considered the reference group. The main outcome measures were preterm birth (PTB), small-for-gestational age (SGA), low birth weight (LBW), macrosomia, large-for-gestational age (LGA), gestational diabetes mellitus (GDM), gestational hypertension, premature rupture and placenta previa.

Results

Overall, 2010 FET cycles with singleton live births were included for analysis. Cycles were allocated to four groups according to the duration of estrogen treatment before progesterone application: ①≤12 days (n=372), ②13-15 days (n=745), ③16-19 days (n=654), ④≥20 days (n=239). The neonatal outcomes, including PTB, SGA, LBW, macrosomia and LGA, were comparable among the groups (P=0.328, P=0.390, P=0.551, P=0.565, P=0.358). The rates of gestational hypertension, premature rupture and placenta previa (P=0.676, P=0.662, P=0.211) were similar among the groups. The rates of GDM among the four groups were 4.0% (15/372), 6.7% (50/745), 6.4% (42/654), and 11.3% (27/239), with statistical significance (P=0.006). After multiple logistic regression analysis, the duration of estrogen treatment did not affect the rate of GDM or other outcomes.

Conclusion

The estrogen treatment duration before progesterone application does not affect neonatal and perinatal outcomes in single frozen blastocyst transfer cycles.

Elevated estradiol levels on hCG trigger day adversely effects on the clinical pregnancy rates of blastocyst embryo transfer but not cleavage-stage embryo transfer in fresh cycles: a retrospective cohort study

Background

Elevated estradiol (E₂) levels are an inevitable outcome of the controlled ovulation hyperstimulation. However, the effect of this change on pregnancy is still uncertain. Our study aimed to analyze the impact of increased serum E₂ at the day of human chorionic gonadotropin (hCG) administration on the clinical outcomes of women with fresh embryo transfer (ET) cycles.

Methods

This study included 3,009 fresh ET cycles from October 2015 to September 2021. Based on the stage of embryos transferred, these cycles were categorized into the cleavage group and blastocyst group. Both groups were then divided into four sets according to E₂ levels when hCG was administered: set 1 (E₂ ≤ 2,000 pg/ml), set 2 (E₂ = 2,001-3,000 pg/ml), set 3 (E₂ = 3,001-4,000 pg/ml), and set 4 (E₂ > 4,000 pg/ml). The primary outcome was the clinical pregnancy rate (CPR). Binary logistics regression analysis was established to explore the association between CPR and E2 levels. Specifically, the threshold effect of serum E2 on CPR was revealed using the two-piecewise linear regression analyses.

Results

The multivariate regression model in the cleavage group showed that patients' CPR in set 4 was 1.59 times higher than those in reference set 1, but the statistical difference was insignificant (P = 0.294). As for the blastocyst group, patients in set 4 had a lower CPR with adjusted ORs of 0.43 (P = 0.039) compared to patients in set 1. The inflection point for the blastocyst group was 39.7 pg/dl according to the results of the two-piecewise linear regression model. When E₂ levels were over the point, the CPR decreased by 17% with every 1 pg/dl increases in serum E₂ (adjusted OR = 0.83, 95% CI [0.72-0.96], P = 0.012).

Conclusions

Elevated E₂ levels (>39.7 pg/dl) on hCG trigger day were associated with decreased CPR in patients with fresh blastocyst ET. However, it had no similar effect on the CPR of patients with fresh cleavage-stage ET.

The effect of peak serum estradiol level during ovarian stimulation on cumulative live birth and obstetric outcomes in freeze-all cycles

Objective

To determine whether the peak serum estradiol (E2) level during ovarian stimulation affects the cumulative live birth rate (CLBR) and obstetric outcomes in freeze-all cycles.

Methods

This retrospective cohort study involved patients who underwent their first cycle of in vitro fertilization followed by a freeze-all strategy and frozen embryo transfer cycles between January 2014 and June 2019 at a tertiary care center. Patients were categorized into four groups according to quartiles of peak serum E2 levels during ovarian stimulation (Q1-Q4). The primary outcome was CLBR. Secondary outcomes included obstetric and neonatal outcomes of singleton and twin pregnancies. Poisson or logistic regression was applied to control for potential confounders for outcome measures, as appropriate. Generalized estimating equations were used to account for multiple cycles from the same patient for the outcome of CLBR.

Results

A total of 11237 patients were included in the analysis. Cumulatively, live births occurred in 8410 women (74.8%). The live birth rate (LBR) and CLBR improved as quartiles of peak E2 levels increased (49.7%, 52.1%, 54.9%, and 56.4% for LBR; 65.1%, 74.3%, 78.4%, and 81.6% for CLBR, from the lowest to the highest quartile of estradiol levels, respectively, P<0.001). Such association remained significant for CLBR after accounting for potential confounders in multivariable regression models, whereas the relationship between LBR and peak E2 levels did not reach statistical significance. In addition, no significant differences were noticed in adverse obstetric and neonatal outcomes (gestational diabetes mellitus, pregnancy-induced hypertension, preeclampsia, placental disorders, preterm birth, low birthweight, and small for gestational age) amongst E2 quartiles for either singleton or twin live births, both before and after adjustment.

Conclusion

In freeze-all cycles, higher peak serum E2 levels during ovarian stimulation were associated with increased CLBR, without increasing the risks of adverse obstetric and neonatal outcomes.

Maternal and obstetric outcomes are influenced by developmental stage and cryopreservation of transferred embryos after clomiphene citrate-based minimal stimulation IVF

STUDY QUESTION

Is the embryo transfer (ET) method associated with maternal and perinatal outcomes after minimal stimulation IVF using clomiphene citrate (CC)?

SUMMARY ANSWER

The incidence of pregnancy complications and adverse perinatal outcomes was influenced by the developmental stage (cleavage versus blastocyst stages) and cryopreservation (fresh versus vitrified) of the transferred embryos.

WHAT IS KNOWN ALREADY

Pregnancies resulting from IVF are associated with higher risks of adverse perinatal outcomes compared to natural conceptions; therefore, the next focus in reproductive medicine should be to assess whether these increased risks are attributable to IVF. Pregnancy complications and perinatal outcomes should be considered in addition to pregnancy outcomes when selecting the ET method, however, studies that describe the influence of transfer methods on perinatal and maternal outcomes are limited.

STUDY DESIGN, SIZE, DURATION

This study retrospectively analysed a large single-centre cohort. The clinical records of 36 827 women who underwent oocyte retrieval (during a CC-based minimal stimulation cycle) followed by their first ET at the fertility treatment centre between January 2008 and December 2017 were retrospectively analysed. The patients underwent a single fresh cleavage-stage ET (SFCT), single vitrified-warmed cleavage-stage ET (SVCT) or single vitrified-warmed blastocyst transfer (SVBT). This study only included one cycle per patient.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocyte retrieval was performed following CC-based minimal ovarian stimulation. The embryos were transferred 2–3 days after retrieval or vitrified at the cleavage or blastocyst stage. The vitrified embryos were then warmed and transferred within the natural cycles. Pregnancy complications and perinatal outcomes were stratified according to the transfer methods used. Multivariate logistic regression analysis was performed to evaluate the effect of ET methods on the prevalence of pregnancy complications and congenital anomalies.

MAIN RESULTS AND THE ROLE OF CHANCE

The rates of clinical pregnancy and delivery were significantly different among the groups. We analysed pregnancy complications in 7502 singleton births (SFCT, 3395 cycles; SVCT, 586 cycles; and SVBT, 3521 cycles). Multivariate logistic regression analysis revealed that the adjusted odds ratio (AOR) for hypertensive disorders in pregnancy was significantly lower in the SVBT group than in the SFCT group [AOR, 0.72; 95% CI, 0.56–0.92]. The AOR for low-lying placenta was lower in the SVBT group than in the SFCT group (AOR, 0.34; 95% CI, 0.19–0.60). The AOR for placenta previa was lower in the SVCT and SVBT groups than in the SFCT group (AOR, 0.21; 95% CI, 0.07–0.58 versus AOR, 0.53; 95% CI, 0.38–0.75, respectively). A total of 7460 follow-up data on neonatal outcomes was analysed. The AOR for preterm delivery was lower in the SVBT group than in the SFCT group (AOR, 0.78; 95% CI, 0.64–0.94). The AOR for low birthweight was significantly lower after SVCT and SVBT than after SFCT (AOR, 0.68; 95% CI, 0.46–0.98 versus AOR, 0.57; 95% CI, 0.48–0.66, respectively). The AOR for small for gestational age was lower in the SVCT and SVBT groups than in the SFCT group (AOR, 0.68; 95% CI, 0.46–0.98 versus AOR, 0.44; 95% CI, 0.36–0.55, respectively). The AOR for large for gestational age babies was higher in the SVBT group than in the SFCT group (AOR, 1.88; 95% CI, 1.62–2.18). The incidence of each congenital anomaly was similar among the groups.

LIMITATIONS, REASONS FOR CAUTION

The study data were collected through self-reported parental questionnaires on maternal and neonatal outcomes. Our findings were not compared with the incidence of pregnancy complications and congenital anomalies in natural pregnancies. Furthermore, this study was retrospective in nature; therefore, further studies are required to ascertain the generalizability of these findings to other clinics with different protocols and/or different patient demographics.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrated reassuring outcomes for SVBT (in terms of a lower incidence of pregnancy complications) compared to SFCT. Our findings provide valuable knowledge that will help improve perinatal and maternal outcomes in CC-based stimulation and inform couples of the possible benefits and risks of each type of ET method.

STUDY FUNDING/COMPETING INTEREST(S)

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Further evidence that a supraphysiologic estradiol level during ovarian stimulation affects birthweight: findings of fresh and frozen embryo transfer with comparable estradiol levels on human chorionic gonadotropin trigger

Studies have reported a supraphysiologic estradiol (E2) level during ovarian stimulation may be related to low birthweight after fresh embryo transfer (ET), but whether a high E2 level in the stimulation cycle affects birthweight via frozen ET remained controversial. The study was to investigate whether a supraphysiologic E2 level in ovarian stimulation cycle affects birth weight in infants conceived via subsequent FET. In this retrospective cohort study, 2525 singletons conceived via FET and 2668 singletons conceived via fresh ET were analyzed. The birthweight and incidences of small for gestational age (SGA) in infants conceived via FET in groups with low and high levels of E2 did not differ significantly. Multivariate analyses showed that the peak E2 level was not predictive of SGA in infants conceived via FET. Singletons conceived via fresh ET had a higher risk of SGA than those conceived via FET even after comparable previous exposure to a high level of E2 > 3000 pg/mL. Our study results indicated that the increased risk of SGA was at least partly a result of the supraphysiologic E2 exposure to the intrauterine environment.

Association between serum oestradiol level on the hCG administration day and neonatal birthweight after IVF-ET among 3659 singleton live births

Oestradiol, an important hormone in follicular development and endometrial receptivity, is closely related to clinical outcomes of fresh in vitro fertilization-embryo transfer (IVF-ET) cycles. A supraphysiologic E2 level is inevitable during controlled ovarian hyper-stimulation (COH), and its effect on the outcome of IVF-ET is controversial. The aim of this retrospective study is to evaluate the association between elevated serum oestradiol (E2) levels on the day of human chorionic gonadotrophin (hCG) administration and neonatal birthweight after IVF-ET cycles. The data of 3659 infertile patients with fresh IVF-ET cycles were analysed retrospectively between August 2009 and February 2017 in First Hospital of Zhengzhou University. Patients were categorized by serum E2 levels on the day of hCG administration into six groups: group 1 (serum E₂ levels ≤ 1000 pg/mL, n = 230), group 2 (serum E2 levels between 1001 and 2000 pg/mL, n = 524), group 3 (serum E₂ levels between 2001 and 3000 pg/mL, n = 783), group 4 (serum E₂ levels between 3001 and 4000 pg/mL, n = 721), group 5 (serum E2 levels between 4001 and 5000 pg/mL, n = 548 ), and group 6 (serum E2 levels > 5000 pg/mL, n = 852). Univariate linear regression was used to evaluate the independent correlation between each factor and outcome index. Multiple logistic regression was used to adjust for confounding factors. The LBW rates were as follows: 3.0% (group 1), 2.9% (group 2), 1.9% (group 3), 2.9% (group 4), 2.9% (group 5), and 2.0% (group 6) (P = 0.629), respectively. There were no statistically significant differences in the incidences of neonatal LBW among the six groups. We did not detect an association between peak serum E2 level during ovarian stimulation and neonatal birthweight after IVF-ET. The results of this retrospective cohort study showed that serum E2 peak levels during ovarian stimulation were not associated with birth weight during IVF cycles. In addition, no association was found between higher E2 levels and increased LBW risk. Our observations suggest that the hyper-oestrogenic milieu during COS does not seem to have adverse effects on the birthweight of offspring after IVF. Although this study provides some reference, the obstetric-related factors were not included due to historical reasons. The impact of the high estrogen environment during COS on the birth weight of IVF offspring still needs future research.

Decreased Endometrial Thickness Is Associated With Higher Risk of Neonatal Complications in Women With Polycystic Ovary Syndrome

PURPOSE

To evaluate the association of endometrial thickness (EMT) with obstetric and neonatal outcomes in women with polycystic ovary syndrome (PCOS).

METHODS

A total of 1755 subfertile PCOS women with singleton livebirths after frozen-thawed embryo transfer were included between January 2009 and September 2019. Main obstetric outcomes were hypertensive disorders in pregnancy and abnormal placentation. Main neonatal outcomes were preterm birth (PTB), low birthweight (LBW) and small-for-gestational age (SGA). Crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were estimated by univariate and multivariate logistic regression analyses.

RESULTS

Each millimeter decrease in EMT was related to a 9% (adjusted OR 1.09, 95% CI 1.00-1.19; P = 0.053), 14% (adjusted OR 1.14, 95% CI 1.02-1.28; P = 0.002) and 22% (adjusted OR 1.22, 95% CI 1.07-1.38; P = 0.003) higher risk of PTB, LBW and SGA, respectively. Compared to women with EMT >13 mm, women with EMT ≤8 mm also had significantly higher risk of PTB (adjusted OR 3.79, 95% CI 1.53-9.39; P = 0.004), LBW (adjusted OR 4.33, 95% CI 1.39-13.50; P = 0.012) and SGA (adjusted OR 6.38, 95% CI 1.78-22.83; P = 0.004). These associations remained consistent in further subgroup analysis by endometrial preparation regimen and in sensitivity analyses among nulligravida women or women without adverse obstetric outcomes. No significant differences were found in the incidence of several pregnancy complications across EMT categories.

CONCLUSION

Decreased EMT was independently associated with increased risk of PTB, LBW and SGA in women with PCOS.