Risk of pre-eclampsia after fresh or frozen embryo transfer in patients undergoing oocyte donation

Pregnancies through oocyte donation. A mini review of pathways involved in placental dysfunction

Pregnancies resulting from assisted reproductive techniques (ART) are increasingly prevalent worldwide. While most pregnancies conceived through in-vitro fertilization (IVF) progress without complications, mounting evidence suggests that these pregnancies are at a heightened risk of adverse perinatal outcomes. Specifically, IVF pregnancies involving oocyte donation have garnered attention due to numerous reports indicating an elevated risk profile for pregnancy-related complications within this subgroup of patients. The precise mechanisms contributing to this increased risk of complications remain incompletely understood. Nonetheless, it is likely that they are mediated by an abnormal immune response at the fetal-maternal interface. Additionally, these outcomes may be influenced by baseline patient characteristics, such as the etiology of infertility, absence of corpus luteum, and variations in endometrial preparation protocols, among other factors. This review aims to succinctly summarize the most widely accepted mechanisms that potentially contribute to the onset of placental dysfunction in pregnancies conceived through oocyte donation.

Comparing the occurrence rate of gestational hypertension during pregnancy with frozen embryo transfer and natural pregnancy

Introduction

Recent researches have indicated that pregnancies with frozen embryo transfer are associated with the increment of risk of maternal and neonatal complications, especially hypertension during pregnancy. The present study aimed to compare the occurrence rate of gestational hypertension in pregnancy with frozen embryo transfer and normal pregnancy.

Materials and Methods

This research, as a retrospective cross-sectional study, was performed on pregnant women with frozen embryo transfer (n = 97) and women with normal pregnancies (n = 164) referring to medical centers under the supervision of Ahvaz University of Medical Sciences in 2021. Women aged 18-35 were included in the study after week 20th of pregnancy. Maternal and neonatal outcomes including hypertensive disorders of pregnancy (including gestational hypertension and preeclampsia), preterm birth (before the week 37th), low birth weight (lower than 2500 g), neonatal asphyxia (Apgar score >7 in minute 5th), intrauterine growth restriction (IUGR) and bleeding in the first trimester of pregnancy were evaluated. The association between frozen embryo transfer and pregnancy outcomes was evaluated using multiple logistic regressions.

Results

The findings of this study indicated that pregnancy hypertension was observed in 23 people (23.7%) from the frozen embryo transfer group vs. 18 people (11.0%) from the normal pregnancy group (P = 0.006). Frozen embryo transfer pregnancy has a higher risk of gestational hypertension (OR = 2.521, 95% CI: 1.281-4.962; P = 0.007), preterm birth (OR = 2.264, 95% CI: 1.335-3.840; P = 0.002), and low birth weight (OR = 2.017, 95% CI: 1.178-3.455; P = 0.011). However, the incidence of birth asphyxia (P = 0.850), intrauterine growth restriction (P = 0.068), first-trimester bleeding (P = 0.809), and placenta accreta (P = 0.143) did not show a significant difference between two types of normal pregnancy and frozen embryo transfer pregnancy.

Conclusion

Frozen embryo transfer pregnancy was associated with a higher risk of maternal and neonatal complications, hypertension, preterm birth, and low birth weight compared to natural and spontaneous pregnancies.

Evidence-Based Pre-Pregnancy Counseling for Oocyte Donation Pregnancies: a Systematic Review and Guide for Physicians

It is well known that oocyte donation (OD) pregnancies are associated with higher complication rates compared to autologous pregnancies. However, evidence-based information for pre-pregnancy counseling designed for health care workers is scarce. Therefore, a systematic literature search was performed to find articles that address pre-pregnancy counseling before OD.A systematic search was conducted in September 2020 in various databases, including PubMed and Embase. Nine (systematic) reviews and meta-analyses were included that reported on pre-pregnancy advice in OD pregnancies.Studies are consistent in documenting a higher risk for hypertensive disorders, cesarean section, preterm birth, postpartum hemorrhage, and low birth weight. Based on these complications, pre-pregnancy advice is mentioned in all included systematic reviews to prevent complications in the next pregnancy. All studies recommend counseling women on the increased risk of complications during OD pregnancy. Other recommendations include the prophylactic use of aspirin in pregnancy and restriction to single embryo transfer. Individualized appropriate surveillance and management strategies should be considered for every patient achieving pregnancy by OD.In conclusion, we provide a summary of the most important outcomes in OD pregnancies, and thereby offer a guide for pre-pregnancy counseling.

Health of 2-year-old children born after vitrified oocyte donation in comparison with peers born after fresh oocyte donation

STUDY QUESTION

Does oocyte vitrification adversely affect the health of 2-year-old children compared with peers born after use of fresh oocytes in a donation programme?

SUMMARY ANSWER

The growth and health of 2-year-old children born after oocyte vitrification are similar to those of peers born after use of fresh oocytes.

WHAT IS KNOWN ALREADY

Although oocyte vitrification is a well-established procedure in ART, the evidence on its safety for offspring is limited. Currently, no disadvantageous effects of oocyte vitrification have been shown in terms of obstetric and neonatal outcome. However, no data beyond the neonatal period are available to date.

STUDY DESIGN, SIZE, DURATION

A combined retrospective and prospective observational study was performed in a tertiary reproductive centre. The retrospective data were available in our extensive database of children born after ART. Donor cycles with an oocyte retrieval between January 2010 and March 2017 and a fresh embryo transfer resulting in the livebirth of a singleton were selected from the established oocyte donation programme. Fresh or vitrified oocytes were used in the donor cycles and all pregnancies in oocyte recipients were achieved after ICSI. Only children residing in Belgium were eligible for follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Biometric and health parameters of 72 children born after oocyte vitrification were compared with those of 41 children born after use of a fresh oocyte. Data were collected by means of questionnaires and physical examinations at the age of 21–30 months. The primary outcome measures were anthropometry and health at 2 years of age.

MAIN RESULTS AND THE ROLE OF CHANCE

Length, weight, BMI, head circumference, left arm circumference and waist circumference at the age of 2 years were comparable between the vitrification and fresh group, also after adjustment for treatment, and maternal and neonatal characteristics (all P > 0.05). Health of the children in terms of hospital admission and surgical intervention rates were comparable between the vitrification and fresh group (both P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

Although the current study is the largest series describing health parameters beyond the neonatal period, the small numbers still preclude definite conclusions.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides the first evidence indicating that oocyte vitrification does not adversely affect the growth and health of offspring beyond the neonatal period.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Methusalem grants and by grants from Wetenschappelijk Fonds Willy Gepts, all issued by the Vrije Universiteit Brussel. All co-authors declared no conflict of interest in relation to this work. Both the Centre for Reproductive Medicine and the Centre for Medical Genetics from the UZ Brussel have received several educational grants from IBSA, Ferring, MSD and Merck for either research on oocyte vitrification or for establishing the database for follow-up research and organizing the data collection.

The freeze-all strategy after IVF: which indications?

The freeze-all strategy is gaining popularity worldwide as an alternative to the conventional fresh embryo transfer. It consists of cryopreservation of the entire embryo cohort and the embryo transfer in a subsequent cycle that takes place separately from ovarian stimulation. The freeze-all strategy was initially a 'rescue' strategy for women at high risk of ovarian hyperstimulation syndrome; however, this approach has been extended to other indications as a scheduled strategy to improve implantation rates. This assumes that ovarian stimulation can alter endometrial receptivity in fresh cycles owing to the effect of supraphysiological levels of steroids on endometrial maturation. The procedure, however, has not been associated with increased live birth rates in all infertile couples, and concerns have been raised about the occurrence of several adverse perinatal outcomes. It is, therefore, crucial to identify in which subgroups of patients a freeze-all strategy could be beneficial. The aim of this review is to summarize current scientific research in this field to highlight potential indications for this strategy and to guide clinicians in their daily practice.

Which is better for mothers and babies: fresh or frozen-thawed blastocyst transfer?

BACKGROUND

In recent years, there have been many reports on the pregnancy outcomes of fresh blastocyst transfer (BT) and frozen-thawed BT, but the conclusions are controversial and incomplete. To compare the pregnancy outcomes, maternal complications and neonatal outcomes of fresh and frozen-thawed BT in the context of in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) cycles, we conducted a meta-analysis.

METHODS

A meta-analysis was conducted by searching the PubMed, Embase, and Cochrane Library databases through May 2020. Data were extracted independently by two authors.

RESULTS

Fifty-four studies, including 12 randomized controlled trials (RCTs), met the inclusion criteria. Fresh BT was associated with a lower implantation rate, pregnancy rate, ongoing pregnancy rate, and clinical pregnancy rate and higher ectopic pregnancy rate than frozen-thawed BT according to the results of the RCTs. The risks of moderate or severe ovarian hyperstimulation syndrome, placental abruption, placenta previa and preterm delivery were higher for fresh BT than for frozen-thawed BT. The risk of pregnancy-induced hypertension and pre-eclampsia was lower for fresh BT; however, no significant differences in risks for gestational diabetes mellitus and preterm rupture of membrane were found between the two groups. Compared with frozen-thawed BT, fresh BT appears to be associated with small for gestational age and low birth weight. No differences in the incidences of neonatal mortality or neonatal malformation were observed between fresh and frozen-thawed BT.

CONCLUSIONS

At present there is an overall slight preponderance of risks in fresh cycles against frozen, however individualization is required and current knowledge does not permit to address a defintive response.

The ART of frozen embryo transfer: back to nature!

The implementation of cryopreservation-techniques in the IVF laboratory and the improved survival rates of oocytes, cleavage and blastocyst stage embryos have led to a significant increase in the number of frozen-thawed embryo transfer cycles (FET). FETs can be planned either in a 'pure' natural cycle, a modified natural cycle, a stimulated cycle or a hormonal replacement therapy cycle and the optimal means to prepare the endometrium for frozen embryo transfer is a topic of ongoing controversy. Recent findings report an increased risk of hypertensive disorders if pregnancy is achieved in a frozen embryo transfer cycle without an existing corpus luteum. Therefore, the question of how to prepare the endometrium has gained even more importance and taken on a new dimension as it should not simply be reduced to the basic question of 'which approach will result in superior pregnancy rates?' but instead 'which approach will result in the best pregnancy rates and the safest outcome for mother and baby?'. The aim of this review is to summarize and critically appraise the existing data on the different approaches of endometrial preparation for frozen embryo transfer with a special focus on the 'pure' natural cycle.

In vitro fertilization and risk for hypertensive disorders of pregnancy: associations with treatment parameters

BACKGROUND

Although in vitro fertilization has been associated with an increased risk for hypertensive disorders of pregnancy, the association of risk with in vitro fertilization treatment parameters is unclear.

OBJECTIVE

To evaluate risk for hypertensive disorders of pregnancy by maternal fertility status and in vitro fertilization treatment parameters.

MATERIALS AND METHODS

Women in 8 states who underwent in vitro fertilization resulting in a live birth during 2004-2013 were linked to their infant's birth certificates. A 10:1 sample of births from non-in vitro fertilization deliveries were selected for comparison. Those with an indication of infertility treatment on the birth certificate were categorized as subfertile and omitted from the study population; all others were categorized as fertile. The in vitro fertilization pregnancies were additionally categorized by oocyte source (autologous versus donor) and embryo state (fresh versus thawed). Both the fertile and in vitro fertilization births were limited to singletons only, and the in vitro fertilization pregnancies were limited to those using partner sperm. Hypertensive disorders of pregnancy (including gestational hypertension and preeclampsia) were identified from the birth certificate, modeled using logistic regression, and reported as adjusted odds ratios and 95% confidence intervals. For analyses of in vitro fertilization pregnancies from autologous oocytes-fresh embryos, the reference group was fertile women (subgroup analysis 1). For analyses within the in vitro fertilization group, the reference group was autologous oocytes-fresh embryos (subgroup analysis 2).

RESULTS

The study population included 1,465,893 pregnancies (1,382,311 births to fertile women and 83,582 births to in vitro fertilization-treated women). Compared to fertile women, in vitro fertilization-treated women with autologous-fresh cycles were not at increased risk for hypertensive disorders of pregnancy (adjusted odds ratio, 1.04; 95% confidence interval, 0.99, 1.08). Among in vitro fertilization births (subgroup analysis 2), the risk for hypertensive disorders of pregnancy was increased for the autologous-thawed (adjusted odds ratio, 1.30; 95% confidence interval, 1.20, 1.40); donor-fresh (adjusted oddds ratio, 1.92; 95% confidence interval, 1.71, 2.15); and donor-thawed (adjusted odds ratio, 1.70; 95% confidence interval, 1.47, 1.96) groups. Excluding women with pregestational diabetes or chronic hypertension as well as adjusting for body mass index and infertility diagnoses did not substantially change the results. When stratified by <34 weeks (early-onset hypertensive disorders of pregnancy) versus ≥34 weeks (late-onset hypertensive disorders of pregnancy), only the donor-fresh group had an increased risk of early-onset hypertensive disorders of pregnancy, but the risks for all other oocyte source-embryo state groups compared to autologous-fresh were increased for late-onset hypertensive disorders of pregnancy.

CONCLUSION

The risk for hypertensive disorders of pregnancy is increased for in vitro fertilization-treated women in pregnancies conceived via frozen embryo transfer (with both autologous or donor oocyte) and fresh donor oocyte embryo transfer. No increase in risk was seen with autologous oocyte-fresh embryo transfers in vitro fertilization cycles. Excluding women with pregestational diabetes or chronic hypertension as well as adjusting for body mass index and infertility diagnoses did not substantially change the results.

Higher rate of early-onset preeclampsia in pregnancies following oocyte donation according to increasing maternal age

OBJECTIVE

To assess the influence of maternal age on the incidence of early-onset preeclampsia requiring delivery before 34 weeks of gestation in pregnancies obtained after oocyte donation.

METHODS

We carried out a prospective cohort analysis of 431 single and twin pregnancies, admitted to 3 Tertiary Referral Hospital in Northern Italy between 2008 and 2017. The rate of early-onset PE was calculated and stratified according to maternal age (from 30 to 49 years). A reference population of 11,197 single pregnancies collected prospectively at the first trimester of pregnancy in the same geographic area of Italy and in same hospitals was used to calculate the expected incidence of early-onset PE.

RESULTS

In women who delivered after 24 weeks of gestation, the rate of early-onset PE was much higher in oocyte-donation pregnancies, reaching 6.7% (29/431), than the expected rate of 0.5% of the cohort of reference. The mean early PE rate was 4.1% (10/242) in singletons and 10.1% (19/189) in twin pregnancies. According to maternal age, the rate of early PE was 1.16% and 3.12% at 30 years, and 4.98% and 13.14% at 49 years in single and twin pregnancies obtained after oocyte donation, respectively.

CONCLUSION

Pregnancies obtained after oocyte donation delivering after 24 weeks had a higher risk of early-onset PE requiring delivery before 34 weeks of gestation, than the general population. The risk is directly correlated with the increase of maternal age and is also higher in twin pregnancies.