Absent or Excessive Corpus Luteum Number Is Associated With Altered Maternal Vascular Health in Early Pregnancy

Progesterone concentrations on blastocyst transfer day in modified natural cycle frozen embryo transfer cycles

RESEARCH QUESTION

Are serum progesterone concentrations on the day of modified natural cycle (mNC) frozen blastocyst transfer (FET) without luteal phase support (LPS) associated with clinical pregnancy rate (CPR)?

DESIGN

Data were collected between January 2019 and October 2022 as a sub-study of an ongoing randomized controlled trial assessing pregnancy outcomes in mNC-FET. The sub-study included all women (n = 209) randomized to mNC-FET without LPS at the time of data extraction. Participants were aged 18-41 years, had regular menstrual cycles and underwent mNC-FET treatment with single-blastocyst transfer. Associations between the serum progesterone concentration on the day of blastocyst transfer and CPR, pregnancy rate and pregnancy loss rate (PLR) were examined between groups with low and higher progesterone concentrations using the 25th and 10th percentiles as cut-offs. Multivariate logistic regression analyses were performed to adjust for potential confounding factors.

RESULTS

Progesterone concentrations on the day of blastocyst transfer in mNC-FET without LPS ranged from 4.9 to 91.8 nmol/l, with the 25th and 10th percentiles at 29.0 nmol/l and 22.5 nmol/l, respectively. Serum progesterone concentrations did not differ between women with or without a clinical pregnancy (mean [SD] 38.5 [14.0] versus 36.8 [12.4] nmol/l; P = 0.350). Furthermore, the CPR, pregancy rate and PLR were similar in women with low or high progesterone concentrations when using the 25th or the 10th progesterone percentile as cut-off. Multivariate regression analyses showed no association between progesterone concentrations and CPR.

CONCLUSIONS

No association was found between progesterone concentration on the day of blastocyst transfer and pregnancy outcome in women undergoing mNC-FET without progesterone LPS.

Clinical features of preeclampsia and hypertensive disorders in pregnancies after different frozen embryo transfer regimens

OBJECTIVES

To compare whether the clinical features of preeclampsia (PE) or gestational hypertension (GH) were different in pregnancies after a frozen embryo transfer (FET), depending on the FET regimen used.

STUDY DESIGN

A retrospective study including 58 pregnancies with PE and 64 pregnancies with GH, all with singleton live births. Pregnancies were stratified according to the presence or absence of a corpus luteum (CL).

MAIN OUTCOME MEASURES

Clinical characteristics of PE and GH, maternal background factors, postpartum hemorrhage (PPH), key perinatal outcomes.

RESULTS

Among PE patients, no difference was found in the clinical characteristics and in the maternal background factors, when comparing women with a CL to women without a CL. PE patients in the group without a CL had a hemorrhage of > 500 mL or > 1000 mL significantly more often than patients with a CL. Multivariable analyses confirmed this risk. Perinatal outcomes were similar. Among GH patients, there was no difference in the clinical features and maternal background factors, when comparing CL cycles to cycles without a CL. The amount of PPH was higher among the patients without a CL, but the frequency of a > 500 mL or > 1000 mL hemorrhage was similar between groups. No risk increase was seen in multivariable analyses.

CONCLUSIONS

Among FET patients with PE, the risk of PPH wasincreased in pregnancies after cycles without a CL, compared to cycles with a CL. The presence or absence of a CL did noteffectthe severity of PE and GH, the duration of pregnancy or blood pressure levels.

Atrial fibrillation considerations in the fourth trimester (postpartum period)

Postpartum atrial fibrillation is an uncommon but increasingly prevalent tachyarrhythmia that merits special management considerations with regards to the safety and efficacy of anticoagulation, rate and rhythm control as well as drug exposure to infants throughout breastfeeding. In this state-of-the-art review, we examine the demographics of postpartum atrial fibrillation with its associated risk factors, describe the safety of commonly used atrial fibrillation therapies, and discuss important considerations for women considering subsequent pregnancies.

Blood pressure and lipid profiles in children born after ART with frozen embryo transfer

STUDY QUESTION

Are blood pressure (BP) and lipid profiles different between children conceived after ART with frozen embryo transfer (FET), fresh embryo transfer (fresh-ET), and natural conception (NC)?

SUMMARY ANSWER

Girls conceived after FET had significantly higher systolic BP and heart rate compared with girls born after fresh-ET; boys conceived after FET had a slightly more favourable lipid profile compared with boys born after fresh-ET and NC.

WHAT IS KNOWN ALREADY

Children conceived after ART with FET are more often born large for gestational age (LGA). LGA in general increases the risk of obesity, diabetes, and cardiovascular disease later in life. Studies on mice and humans on the whole ART population have raised concerns about premature vascular ageing and higher BP. The cardiovascular health of children born after FET is scarcely explored and the results are diverging.

STUDY DESIGN SIZE DURATION

This study was part of the cohort study 'Health in Childhood following Assisted Reproductive Technology' (HiCART), which included 606 singletons (292 boys) born between December 2009 and December 2013: 200 children were conceived after FET; 203 children were conceived after fresh-ET; and 203 children were conceived naturally and matched for birth year and sex. The study period lasted from January 2019 to September 2021.

PARTICIPANTS/MATERIALS SETTING METHODS

The included children were 7-10 years of age at examination and underwent a clinical examination with anthropometric measurements, pubertal staging, and BP measurement. Additionally, a fasting blood sample was collected and analysed for cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), and triglycerides. Systolic and diastolic BP were converted to standard deviation scores (SDS) using an appropriate reference and accounting for height (SDS) of the child. The three study groups were compared pairwise using a univariate linear regression model. Mean differences were adjusted for confounders using multiple linear regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

Girls and boys conceived after FET had significantly higher birthweight (SDS) compared with naturally conceived peers (mean difference: girls: 0.35, 95% CI (0.06-0.64), boys: 0.35, 95% CI (0.03-0.68)). Girls conceived after FET had significantly higher systolic BP (SDS) and heart rate compared with girls conceived after fresh-ET (adjusted mean difference: systolic BP (SDS): 0.25 SDS, 95% CI (0.03-0.47), heart rate: 4.53, 95% CI (0.94-8.13)). Regarding lipid profile, no significant differences were found between the three groups of girls. For the boys, no significant differences were found for BP and heart rate. Lipid profiles were more favourable in boys born after FET compared with both boys conceived after fresh-ET and NC. All outcomes were adjusted for parity, maternal BMI at early pregnancy, smoking during pregnancy, educational level, birthweight, breastfeeding, child age at examination, and onset of puberty.

LIMITATIONS REASONS FOR CAUTION

The participation rate varied from 18 to 42% in the three groups, and therefore selection bias cannot be excluded. However, extensive non-participant analyses were performed that showed almost no differences in background characteristics between participants and non-participants in the three groups, making selection bias less likely.

WIDER IMPLICATIONS OF THE FINDINGS

The higher birthweight in children conceived after FET was associated with increased systolic BP (SDS) and heart rate in girls conceived after FET compared with fresh-ET. This may be an early indicator of compromised long-term cardiovascular health in this group. The study was not powered to investigate these outcomes and further studies are therefore warranted to confirm the findings.

STUDY FUNDING/COMPETING INTERESTS

The study was funded by the Novo Nordisk Foundation (grant number: NNF18OC0034092, NFF19OC0054340) and Rigshospitalets Forskningsfond. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier: NCT03719703.

The impact of serum estradiol and progesterone levels during implantation on obstetrical complications and perinatal outcomes in frozen embryo transfer

BACKGROUND

This study sought to evaluate obstetric complications and perinatal outcomes in frozen embryo transfer (FET) using either a natural cycle (NC-FET) or a hormone therapy cycle (HT-FET). Furthermore, we investigated how serum levels of estradiol (E2) and progesterone (P4) on the day of and 3 days after embryo transfer (ET) correlated with clinical outcomes in the two groups.

METHODS

We conducted a retrospective, single-center study from January 1, 2015, to December 31, 2019. The study included couples who underwent NC-FET or HT-FET resulting in a singleton live birth. Serum levels of E2 and P4 were measured on the day of and 3 days after ET. The primary outcomes assessed were preterm birth rate, low birth weight, macrosomia, hypertensive disorders in pregnancy, gestational diabetes mellitus, postpartum hemorrhage, and placenta-related complications.

RESULTS

A total of 229 singletons were included, with 49 in the NC-FET group and 180 in the HT-FET group. There were no significant differences in obstetric complications and perinatal outcomes between the two groups. The NC-FET group had significantly higher serum levels of P4 (17.2 ng/mL vs 8.85 ng/mL; p < 0.0001) but not E2 (144 pg/mL vs 147 pg/mL; p = 0.69) on the day of ET. Additionally, 3 days after ET, the NC-FET group had significantly higher levels of both E2 (171 pg/mL vs 140.5 pg/mL; p = 0.0037) and P4 (27.3 ng/mL vs 11.7 ng/mL; p < 0.0001) compared with the HT-FET group.

CONCLUSION

Our study revealed that although there were significant differences in E2 and P4 levels around implantation between the two groups, there were no significant differences in obstetric complications and perinatal outcomes. Therefore, the hormonal environment around implantation did not appear to be the primary cause of differences in obstetric and perinatal outcomes between the two EM preparation methods used in FET.

The impact of fresh versus frozen-thawed embryos on maternal serum analyte levels in IVF singleton and twin pregnancies

PURPOSE

To determine whether embryo cryopreservation is associated with a difference in maternal serum analyte levels in singleton and twin pregnancies conceived via in vitro fertilization (IVF).

METHODS

This was a retrospective cohort study of singleton and twin pregnancies conceived via IVF from a university health system from 01/2014 to 09/2019. Patients with available first and second trimester serum analyte data were included and analyzed separately. Multiple of the median (MoM) values for free β-human chorionic gonadotropin (β-hCG), pregnancy-associated plasma protein A, alpha-fetoprotein (AFP), Inhibin A, and unconjugated estriol (uE3) were compared between two groups: pregnancies conceived after the transfer of fresh embryos versus pregnancies conceived after the transfer of frozen-thawed embryos. Multiple linear regression of log MoM values with F test was performed to adjust for potential confounders.

RESULTS

For singletons, fresh embryos were associated with a lower median first trimester free β-hCG (1.00 MoM vs. 1.14 MoM; parameter estimate [PE] 0.90, 95% CI 0.82-0.99, p = .03) compared to frozen-thawed embryos. Fresh embryos were also associated with a lower median second trimester uE3 (0.93 MoM vs. 1.05 MoM; PE 0.88, CI 0.83-0.95, p = .0004) and AFP (1.02 MoM vs. 1.19 MoM; PE 0.91, CI 0.84-0.99, p = .02) compared to frozen-thawed embryos in singletons. There were no significant differences between median first and second trimester serum analytes in twin pregnancies compared between the two groups.

CONCLUSION

Singleton pregnancies derived from fresh embryos had lower first (free β-hCG) and second (uE3 and AFP) trimester analytes compared to frozen-thawed embryos. Twin pregnancies demonstrated no difference between the groups.

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.

Maternal and neonatal complications after IVF/ICSI-fresh embryo transfer in low-prognosis women under the POSEIDON criteria: a retrospective cohort study

BACKGROUND

Several studies on pregnancy complications of poor ovarian response (POR) patients did not draw a consistent conclusion. The POSEIDON criteria introduces the concept of "low prognosis" and divides POR patients into four groups based on age, AFC and AMH for individualized management. We analyzed low-prognosis population and patients with regular ovarian response, compared maternal and neonatal complications and discussed the relevant risk factors.

METHODS

A retrospective cohort study was conducted of females who achieved a singleton clinical pregnancy after IVF / ICSI-fresh embryo transfer in a single center from January 2014 to March 2019. Participants with low prognosis, as defined by the POSEIDON criteria, were enrolled in the study groups. The controls were defined as AFC ≥ five and number of retrieved oocytes > nine. Maternal and neonatal complications were compared among those groups.

RESULTS

There were 2554 cycles in POSEIDON group 1, 971 in POSEIDON group 2, 141 in POSEIDON group 3, 142 in POSEIDON group 4, and 3820 in Control. Univariate analysis roughly showed that Groups 2 and 4 had an increased tendency of pregnancy complications. Multi-variable generalized estimating equations (GEE) analysis showed that the risks of GDM, total pregnancy loss, and first-trimester pregnancy loss in Groups 2 and 4 were significantly higher than in Control. The risk of hypertensive disorders of pregnancy (HDP) in Groups 2 and 3 increased, and Group 4 had an increased tendency without statistical significance. After classification by age, GEE analysis showed no significant difference in risks of all complications among groups ≥ 35 years. In patients < 35 years, the risk of HDP in POSEIDON group 3 was significantly higher than in controls (< 35 years), and there was no significant increase in the risk of other complications.

CONCLUSION

Compared to patients with regular ovarian response, low-prognosis population have increased tendency of maternal and neonatal complications. In low-prognosis patients, advanced age (≥ 35 years) might be the predominant risk factor for pregnancy complications. In those < 35 years, poor ovarian reserve could contribute to HDP.

Maternal and child-health outcomes in different endometrial preparation methods for frozen-thawed embryo transfer: a retrospective study

The purpose of this study was to analyse the obstetric outcome after frozen embryo transfer depending on the protocol used. The endometrial preparation during frozen embryo transfer (FET) was performed in the natural cycle (NC) with timing based on monitoring of the naturally occurring luteinizing hormone (LH) peak or in human chorionic gonadotropin (hCG)-triggered modified natural cycles (MNC), artificial cycle (AC) with hormone replacement therapy cycle and cycle with ovulation induction (OI). A retrospective cohort study was conducted between 2018 and 2020. Pregnancy, perinatal complications and neonatal outcomes were compared among patients treated during AC or MNC or OI protocols. After adjusting for the effect of gravidity, parity, pre-pregnancy body mass index (BMI) and number of miscarriages, the AC group had higher but not significantly different rates of gestational hypertension, preeclampsia and intrahepatic cholestasis of pregnancy (ICP) than women in OI and MNC groups. Significant differences were observed in the rates of placental adherence (15.30% in AC vs. 9.24% in MNC, p = 0.004) and postpartum haemorrhage (PPH) (24.33% in AC vs. 13.07% in OI, p = 0.003, 24.33% in AC vs. 16.24% in MNC, p = 0.002) among the three groups. In singletons, significant differences were observed in the rates of placental adherence (14.09% in AC vs. 8.57% in MNC, p = 0.002), AC and MNC groups had higher risk of PPH compared with OI group (18.36% in AC vs. 12.38% in MNC, p = 0.042 and 7.69% in OI vs. 18.36% in AC, p = 0.013). Neonatal outcomes were similar among the three groups except risk of small for date infants (0.35% in AC vs. 1.44% in MNC, p = 0.008). These findings are important in view of increasing use of frozen cycles and new policy of freeze-all cycles in in vitro fertilization (IVF). The results suggest a link between the absence of corpus luteum and adverse obstetric outcomes.

Good practice recommendations on add-ons in reproductive medicine†

STUDY QUESTION

Which add-ons are safe and effective to be used in ART treatment?

SUMMARY ANSWER

Forty-two recommendations were formulated on the use of add-ons in the diagnosis of fertility problems, the IVF laboratory and clinical management of IVF treatment.

WHAT IS KNOWN ALREADY

The innovative nature of ART combined with the extremely high motivation of the patients has opened the door to the wide application of what has become known as 'add-ons' in reproductive medicine. These supplementary options are available to patients in addition to standard fertility procedures, typically incurring an additional cost. A diverse array of supplementary options is made available, encompassing tests, drugs, equipment, complementary or alternative therapies, laboratory procedures, and surgical interventions. These options share the common aim of stating to enhance pregnancy or live birth rates, mitigate the risk of miscarriage, or expedite the time to achieving pregnancy.

STUDY DESIGN, SIZE, DURATION

ESHRE aimed to develop clinically relevant and evidence-based recommendations focusing on the safety and efficacy of add-ons currently used in fertility procedures in order to improve the quality of care for patients with infertility.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ESHRE appointed a European multidisciplinary working group consisting of practising clinicians, embryologists, and researchers who have demonstrated leadership and expertise in the care and research of infertility. Patient representatives were included in the working group. To ensure that the guidelines are evidence-based, the literature identified from a systematic search was reviewed and critically appraised. In the absence of any clear scientific evidence, recommendations were based on the professional experience and consensus of the working group. The guidelines are thus based on the best available evidence and expert agreement. Prior to publication, the guidelines were reviewed by 46 independent international reviewers. A total of 272 comments were received and incorporated where relevant.

MAIN RESULTS AND THE ROLE OF CHANCE

The multidisciplinary working group formulated 42 recommendations in three sections; diagnosis and diagnostic tests, laboratory tests and interventions, and clinical management.

LIMITATIONS, REASONS FOR CAUTION

Of the 42 recommendations, none could be based on high-quality evidence and only four could be based on moderate-quality evidence, implicating that 95% of the recommendations are supported only by low-quality randomized controlled trials, observational data, professional experience, or consensus of the development group.

WIDER IMPLICATIONS OF THE FINDINGS

These guidelines offer valuable direction for healthcare professionals who are responsible for the care of patients undergoing ART treatment for infertility. Their purpose is to promote safe and effective ART treatment, enabling patients to make informed decisions based on realistic expectations. The guidelines aim to ensure that patients are fully informed about the various treatment options available to them and the likelihood of any additional treatment or test to improve the chance of achieving a live birth.

STUDY FUNDING/COMPETING INTEREST(S)

All costs relating to the development process were covered from ESHRE funds. There was no external funding of the development process or manuscript production. K.L. reports speakers fees from Merck and was part of a research study by Vitrolife (unpaid). T.E. reports consulting fees from Gynemed, speakers fees from Gynemed and is part of the scientific advisory board of Hamilton Thorne. N.P.P. reports grants from Merck Serono, Ferring Pharmaceutical, Theramex, Gedeon Richter, Organon, Roche, IBSA and Besins Healthcare, speakers fees from Merck Serono, Ferring Pharmaceutical, Theramex, Gedeon Richter, Organon, Roche, IBSA and Besins Healthcare. S.R.H. declares being managing director of Fertility Europe, a not-for-profit organization receiving financial support from ESHRE. I.S. is a scientific advisor for and has stock options from Alife Health, is co-founder of IVFvision LTD (unpaid) and received speakers' fee from the 2023 ART Young Leader Prestige workshop in China. A.P. reports grants from Gedeon Richter, Ferring Pharmaceuticals and Merck A/S, consulting fees from Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos and Merck A/S, speakers fees from Gedeon Richter, Ferring Pharmaceuticals, Merck A/S, Theramex and Organon, travel fees from Gedeon Richter. The other authors disclosed no conflicts of interest.

DISCLAIMER

This Good Practice Recommendations (GPRs) document represents the views of ESHRE, which are the result of consensus between the relevant ESHRE stakeholders and are based on the scientific evidence available at the time of preparation.ESHRE GPRs should be used for information and educational purposes. They should not be interpreted as setting a standard of care or bedeemedinclusive of all proper methods of care, or be exclusive of other methods of care reasonably directed to obtaining the same results.Theydo not replace the need for application of clinical judgement to each individual presentation, or variations based on locality and facility type.Furthermore, ESHRE GPRs do not constitute or imply the endorsement, or favouring, of any of the included technologies by ESHRE.

Impact of Endometrial Preparation on the Maternal and Fetal Cardiovascular Variables of the First Trimester Combined Screening Test

The modality of endometrial preparation for the transfer of frozen-thawed embryos may influence maternal and fetal adaptation to pregnancy and could thus impact the results of the first trimester combined screening test. We conducted a retrospective cross-sectional study on singleton pregnancies achieved by embryo transfer of a single frozen-thawed blastocyst, comparing two different endometrial preparation protocols: natural cycle (n = 174) and hormone replacement therapy (HRT) (n = 122). The primary outcome was the risk of preeclampsia at the first trimester combined screening test. Secondary endpoints included variable reflecting fetal cardiac function (nuchal translucency and fetal heart rate), maternal adaptation (median arterial blood pressure-MAP and uterine arteries pulsatility index-UtA-PI), and placentation (pregnancy associated plasma protein A and placental growth factor). The risk of early preeclampsia was comparable in the two groups (38% vs. a 28%, p = 0.12). However, women in the natural cycle group showed lower fetal heart rate (159 [155-164] vs. 164 [158-168], p = 0.002) and higher UtA-PI (0.96 [0.74-1.18] vs. 0.72 [0.58-0.90], p < 0.001). The frequency of a screening test at high risk for aneuploidies was similar. The modality of transfer of frozen-thawed embryos is associated with changes in the variables reflecting maternal and fetal cardiovascular function.

An appraisal of current embryo transfer strategies

Embryo transfer, one of the most essential procedures in assisted reproductive technology, plays a vital role in the success of in-vitro fertilization and intracytoplasmic sperm injection. During the last decades, the strategies for embryo transfer have changed dramatically. In this review, we evaluate the efficacy and safety of several current embryo transfer strategies including fresh versus frozen embryo transfer, cleavage- versus blastocyst-stage embryo transfer, and single- versus double-embryo transfer. Available evidence indicates that the freeze-only strategy improves the live birth rate after the first embryo transfer in high responders while making no difference in normal responders. The risk of ovarian hyperstimulation syndrome is significantly reduced in the freeze-only strategy. Fresh blastocyst-stage embryo transfer increased live birth rate compared to cleavage-stage embryo transfer. The best embryo transfer strategy is one which tailors to individual circumstances and preferences.

Obstetric and neonatal outcomes after natural versus artificial cycle frozen embryo transfer and the role of luteal phase support: a systematic review and meta-analysis

BACKGROUND

The number of frozen embryo transfers (FET) has increased dramatically over the past decade. Based on current evidence, there is no difference in pregnancy rates when natural cycle FET (NC-FET) is compared to artificial cycle FET (AC-FET) in subfertile women. However, NC-FET seems to be associated with lower risk of adverse obstetric and neonatal outcomes compared with AC-FET cycles. Currently, there is no consensus about whether NC-FET needs to be combined with luteal phase support (LPS) or not. The question of how to prepare the endometrium for FET has now gained even more importance and taken the dimension of safety into account as it should not simply be reduced to the basic question of effectiveness.

OBJECTIVE AND RATIONALE

The objective of this project was to determine whether NC-FET, with or without LPS, decreases the risk of adverse obstetric and neonatal outcomes compared with AC-FET.

SEARCH METHODS

A systematic review and meta-analysis was carried out. A literature search was performed using the following databases: CINAHL, EMBASE, and MEDLINE from inception to 10 October 2022. Observational studies, including cohort studies, and registries comparing obstetric and neonatal outcomes between singleton pregnancies after NC-FET and those after AC-FET were sought. Risk of bias was assessed using the ROBINS-I tool. The quality of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation approach. We calculated pooled odds ratios (ORs), pooled risk differences (RDs), pooled adjusted ORs, and prevalence estimates with 95% CI using a random effect model, while heterogeneity was assessed by the I2.

OUTCOMES

The conducted search identified 2436 studies, 890 duplicates were removed and 1546 studies were screened. Thirty studies (NC-FET n = 56 445; AC-FET n = 57 231) were included, 19 of which used LPS in NC-FET. Birthweight was lower following NC-FET versus AC-FET (mean difference 26.35 g; 95% CI 11.61-41.08, I2 = 63%). Furthermore NC-FET compared to AC-FET resulted in a lower risk of large for gestational age (OR 0.88, 95% 0.83-0.94, I2 = 54%), macrosomia (OR 0.81; 95% CI 0.71-0.93, I2 = 68%), low birthweight (OR 0.81, 95% CI 0.77-0.85, I2 = 41%), early pregnancy loss (OR 0.73; 95% CI 0.61-0.86, I2 = 70%), preterm birth (OR 0.80; 95% CI 0.75-0.85, I2 = 20%), very preterm birth (OR 0.66, 95% CI 0.53-0.84, I2 = 0%), hypertensive disorders of pregnancy (OR 0.60, 95% CI 0.50-0.65, I2 = 61%), pre-eclampsia (OR 0.50; 95% CI 0.42-0.60, I2 = 44%), placenta previa (OR 0.84, 95% CI 0.73-0.97, I2 = 0%), and postpartum hemorrhage (OR 0.43; 95% CI 0.38-0.48, I2 = 53%). Stratified analyses on LPS use in NC-FET suggested that, compared to AC-FET, NC-FET with LPS decreased preterm birth risk, while NC-FET without LPS did not (OR 0.75, 95% CI 0.70-0.81). LPS use did not modify the other outcomes. Heterogeneity varied from low to high, while quality of the evidence was very low to moderate.

WIDER IMPLICATIONS

This study confirms that NC-FET decreases the risk of adverse obstetric and neonatal outcomes compared with AC-FET. We estimate that for each adverse outcome, use of NC-FET may prevent 4 to 22 cases per 1000 women. Consequently, NC-FET should be the preferred treatment in women with ovulatory cycles undergoing FET. Based on very low quality of evidence, the risk of preterm birth be decreased when LPS is used in NC-FET compared to AC-FET. However, because of many uncertainties-the major being the debate about efficacy of the use of LPS-future research is needed on efficacy and safety of LPS and no recommendation can be made about the use of LPS.

Increased Risk of Preeclampsia with Assisted Reproductive Technologies

PURPOSE OF REVIEW

We summarized recent available data to assess the association between assisted reproductive technology (ART) and risk for preeclampsia.

RECENT FINDINGS

The majority of clinical studies supporting the association of preeclampsia and ART are retrospective. Published data from both clinical and pre-clinical studies suggest specific ART procedures may contribute to the increased risk, including in vitro embryo handling and development, hormone stimulation, transfer cycle types, and use of donor oocytes/embryos. Potential mechanisms include epigenetic aberrations leading to abnormal placentation, absence of factors secreted by the corpus luteum, and immunologic responses to allogenic gametes. There is an increased risk of preeclampsia following ART. Treatment plans that favor reduced preeclampsia risk should be considered for ART pregnancies. To make ART pregnancies safer, additional clinical and animal model studies are needed to elucidate the underpinnings of this risk association.

The influence of embryo stage on obstetric complications and perinatal outcomes following programmed compared to natural frozen-thawed embryo transfer cycles: a systematic review and meta-analysis

Objective

To investigate the effect of embryo stage at the time of transfer on obstetric and perinatal outcomes in programmed frozen-thawed embryo transfer (FET) versus natural FET cycles.

Design

Systematic review and meta-analysis.

Setting

Not applicable.

Patients

Women with programmed frozen-thawed embryo transfer (FET) and natural FET.

Interventions

The PubMed, MEDLINE, and EMBASE databases and the Cochrane Central Register of Controlled Trials (CCRT) were searched from 1983 to October 2022. Twenty-three observational studies were included.

Primary outcome measure

The primary outcomes were hypertensive disorders of pregnancy (HDPs), gestational hypertension and preeclampsia (PE). The secondary outcomes were gestational diabetes mellitus (GDM), placenta previa, postpartum haemorrhage (PPH), placental abruption, preterm premature rupture of membranes (PPROM), large for gestational age (LGA), small for gestational age (SGA), macrosomia, and preterm delivery (PTD).

Results

The risk of HDP (14 studies, odds ratio (OR) 2.17; 95% confidence interval (CI) 1.95-2.41; P<0.00001; I2 = 43%), gestational hypertension (11 studies, OR 1.38; 95% CI 1.15-1.66; P=0.0006; I2 = 19%), PE (12 studies, OR 2.09; 95% CI 1.88-2.32; P<0.00001; I2 = 0%), GDM (20 studies, OR 1.09; 95% CI 1.02-1.17; P=0.02; I2 = 8%), LGA (18 studies, OR 1.11; 95% CI 1.07-1.15; P<0.00001; I2 = 46%), macrosomia (12 studies, OR 1.15; 95% CI 1.07-1.24; P=0.0002; I2 = 31%), PTD (22 studies, OR 1.21; 95% CI 1.15-1.27; P<0.00001; I2 = 49%), placenta previa (17 studies, OR 1.2; 95% CI 1.02-1.41; P=0.03; I2 = 11%), PPROM (9 studies, OR 1.19; 95% CI 1.02-1.39; P=0.02; I2 = 40%), and PPH (12 studies, OR 2.27; 95% CI 2.02-2.55; P <0.00001; I2 = 55%) were increased in programmed FET cycles versus natural FET cycles with overall embryo transfer. Blastocyst transfer had a higher risk of HDP (6 studies, OR 2.48; 95% CI 2.12-2.91; P<0.00001; I2 = 39%), gestational hypertension (5 studies, OR 1.87; 95% CI 1.27-2.75; P=0.002; I2 = 25%), PE (6 studies, OR 2.23; 95% CI 1.93-2.56; P<0.00001; I2 = 0%), GDM (10 studies, OR 1.13; 95% CI 1.04-1.23; P=0.005; I2 = 39%), LGA (6 studies, OR 1.14; 95% CI 1.07-1.21; P<0.0001; I2 = 9%), macrosomia (4 studies, OR 1.15; 95% CI 1.05-1.26; P<0.002; I2 = 68%), PTD (9 studies, OR 1.43; 95% CI 1.31-1.57; P<0.00001; I2 = 22%), PPH (6 studies, OR 1.92; 95% CI 1.46-2.51; P<0.00001; I2 = 55%), and PPROM (4 studies, OR 1.45; 95% CI 1.14-1.83; P=0.002; I2 = 46%) in programmed FET cycles than in natural FET cycles. Cleavage-stage embryo transfers revealed no difference in HDPs (1 study, OR 0.81; 95% CI 0.32-2.02; P=0.65; I2 not applicable), gestational hypertension (2 studies, OR 0.85; 95% CI 0.48-1.51; P=0.59; I2 = 0%), PE (1 study, OR 1.19; 95% CI 0.58-2.42; P=0.64; I2not applicable), GDM (3 study, OR 0.79; 95% CI 0.52-1.20; P=0.27; I2 = 21%), LGA (1 study, OR 1.15; 95% CI 0.62-2.11; P=0.66; I2not applicable), macrosomia (1 study, OR 1.22; 95% CI 0.54-2.77; P=0.64; I2 not applicable), PTD (2 studies, OR 1.05; 95% CI 0.74-1.49; P=0.79; I2 = 0%), PPH (1 study, OR 1.49; 95% CI 0.85-2.62; P=0.17; I2not applicable), or PPROM (2 studies, OR 0.74; 95% CI 0.46-1.21; P=0.23; I2 = 0%) between programmed FET cycles and natural FET cycles.

Conclusions

The risks of HDPs, gestational hypertension, PE, GDM, LGA, macrosomia, SGA, PTD, placenta previa, PPROM, and PPH were increased in programmed FET cycles versus natural FET cycles with overall embryo transfer and blastocyst transfer, but the risks were not clear for cleavage-stage embryo transfer.

Clinical pregnancy rate for frozen embryo transfer with HRT: a randomized controlled pilot study comparing 1 week versus 2 weeks of oestradiol priming

RESEARCH QUESTION

Does a frozen-embryo transfer in an artificially-prepared endometrium (FET-HRT) cycle yield similar clinical pregnancy rate with 7 days of oestrogen priming compared to 14 days?

DESIGN

This is a single-centre, randomized, controlled, open-label pilot study. All FET-HRT cycles were performed in a tertiary centre between October 2018 and January 2021. Overall, 160 patients were randomized, with a 1:1 allocation, into two groups of 80 patients each: group A (7 days of E2 prior to P4 supplementation) and group B (14 days of E2 prior to P4 supplementation). Both groups received single blastocyst stage embryos on the 6th day of vaginal P4 administration. The primary outcome was the feasibility of such strategy assessed as clinical pregnancy rate, secondary outcomes were biochemical pregnancy rate, miscarriage rate, live birth rate and serum hormone levels on the day of FET. Chemical pregnancy was assessed by an hCG blood test 12 days after FET and clinical pregnancy was confirmed by transvaginal ultrasound at 7 weeks.

RESULTS

The analysis included 160 patients who were randomly assigned to either group A or group B on the seventh day of their FET-HRT cycle if the measured endometrial thickness was above 6.5 mm. Following screening failures and of drop-outs, 144 patients were finally included both in group A (75 patients) or group B (69 patients). Demographic characteristics for both groups were comparable. The biochemical pregnancy rate was 42.5% and 48.8% for group A and group B, respectively (p 0.526). Regarding the clinical pregnancy rate at 7 weeks, no statistical difference was observed (36.3% vs 46.3% for group A and group B, respectively, p = 0.261). The secondary outcomes of the study (biochemical pregnancy, miscarriage, and live birth rate) were comparable between the two groups for IIT analysis, as well as the P4 values on the day of FET.

CONCLUSIONS

In a frozen embryo transfer cycle, performed with artificial preparation of the endometrium, 7 versus 14 days of oestrogen priming are comparable, in terms of clinical pregnancy rate; the advantages of a seven-day protocol include the shorter time to pregnancy, reduced exposure to oestrogens, and more flexibility of scheduling and programming, and less probability to recruit a follicle and have a spontaneous LH surge. It is important to keep in mind that this study was designed as a pilot trial with a limited study population as such it was underpowered to determine the superiority of an intervention over another; larger-scale RCTs are warranted to confirm our preliminary results.

TRIAL REGISTRATION

Clinical trial number: NCT03930706.

Can Cryopreservation in Assisted Reproductive Technology (ART) Induce Epigenetic Changes to Gametes and Embryos?

Since the birth of Louise Brown in 1978, more than nine million children have been conceived using assisted reproductive technologies (ARTs). While the great majority of children are healthy, there are concerns about the potential epigenetic consequences of gametes and embryo manipulation. In fact, during the preimplantation period, major waves of epigenetic reprogramming occur. Epigenetic reprogramming is susceptible to environmental changes induced by ovarian stimulation, in-vitro fertilization, and embryo culture, as well as cryopreservation procedures. This review summarizes the evidence relating to oocytes and embryo cryopreservation and potential epigenetic regulation. Overall, it appears that the stress induced by vitrification, including osmotic shock, temperature and pH changes, and toxicity of cryoprotectants, might induce epigenetic and transcriptomic changes in oocytes and embryos. It is currently unclear if these changes will have potential consequences for the health of future offspring.

Higher risk of pre-eclampsia and other vascular disorders with artificial cycle for frozen-thawed embryo transfer compared to ovulatory cycle or to fresh embryo transfer following in vitro fertilization

Background

Risks of maternal morbidity are known to be reduced in pregnancies resulting from frozen embryo transfer (FET) compared to fresh-embryo transfer (fresh-ET), except for the risk of pre-eclampsia, reported to be higher in FET pregnancies compared to fresh-ET or natural conception. Few studies have compared the risk of maternal vascular morbidities according to endometrial preparation for FET, either with ovulatory cycle (OC-FET) or artificial cycle (AC-FET). Furthermore, maternal pre-eclampsia could be associated with subsequent vascular disorders in the offspring.

Methods

A 2013-2018 French nationwide cohort study comparing maternal vascular morbidities in 3 groups of single pregnancies was conducted: FET with either OC or AC preparation, and fresh-ET. Data were extracted from the French National Health System database. Results were adjusted for maternal characteristics and infertility (age, parity, smoking, obesity, history of diabetes or hypertension, endometriosis, polycystic ovary syndrome and premature ovarian insufficiency).

Results

A total of 68025 single deliveries were included: fresh-ET (n=48152), OC-FET (n=9500), AC-FET (n=10373). The risk of pre-eclampsia was higher in AC-FET compared to OC-FET and fresh-ET groups in univariate analysis (5.3% vs. 2.3% and 2.4%, respectively, P<0.0001). In multivariate analysis the risk was significantly higher in AC-FET compared to fresh-ET: aOR=2.43 [2.18-2.70], P<0.0001). Similar results were observed for the risk of other vascular disorders in univariate analysis (4.7% vs. 3.4% and 3.3%, respectively, P=0.0002) and in multivariate analysis (AC-FET compared to fresh-ET: aOR=1.50 [1.36-1.67], P<0.0001). In multivariate analysis, the risk of pre-eclampsia and other vascular disorders were comparable in OC-FET and fresh-ET: aOR=1.01 [0.87-1.17, P= 0.91 and aOR=1.00 [0.89-1.13], P=0.97, respectively).Within the group of FET, the risks of pre-eclampsia and other vascular disorders in multivariate analysis were higher in AC-FET compared to OC-FET (aOR=2.43 [2.18-2.70], P<0.0001 and aOR=1.5 [1.36-1.67], P<0.0001, respectively).

Conclusion

This nationwide register-based cohort study highlights the possibly deleterious role of prolonged doses of exogenous estrogen-progesterone supplementation on gestational vascular pathologies and the protective role of the corpus luteum present in OC-FET for their prevention. Since OC-FET has been demonstrated not to strain the chances of pregnancy, OC preparation should be advocated as first-line preparation in FET as often as possible in ovulatory women.

The likelihood of a healthy live birth after frozen embryo transfer with endometrium prepared by natural ovulation regimen vs programmed regimen: a propensity-score matching study

BACKGROUND

The number of frozen embryo transfer cycles is increasing, but the optimal method of endometrial preparation for frozen embryo transfer remains controversial. Few studies have investigated the healthy live birth outcome after the natural ovulation regimen vs the programmed regimen.

OBJECTIVE

This study aimed to explore whether the likelihood of a healthy live birth after frozen embryo transfer differs between the natural ovulation regimen and the programmed regimen.

STUDY DESIGN

We conducted a retrospective cohort study including 7824 ovulatory women who underwent the first frozen embryo transfer cycle of single-blastocyst transfer with endometrial preparation by natural ovulation regimen vs programmed regimen, between June 2017 and June 2021. Propensity score matching was used to control for confounding variables in a 1:1 ratio. The primary outcome was healthy live birth, defined as birth of a live, singleton infant born at term, with an appropriate birthweight for gestational age.

RESULTS

The natural ovulation regimen resulted in a higher probability of achieving healthy live birth compared with the programmed regimen (35.8% vs 30.6%; P<.0001). In addition, a higher rate of singleton live birth was observed after the natural ovulation regimen relative to the programmed regimen (49.6% vs 45.7%; P=.003). Women with the natural ovulation regimen were also less likely to experience clinical pregnancy loss (16.0% vs 19.7%; P=.005) and hypertensive disorders of pregnancy (3.9% vs 6.0%; P=.004) compared with women with the programmed regimen. Singletons born after the programmed regimen had greater mean birthweight (3441.50±539.97 vs 3394.96±503.87; P=.020) and higher risk of being large for gestational age (23.3% vs 18.7%; P=.003) than those conceived after the natural ovulation regimen.

CONCLUSION

The natural ovulation regimen may be superior to the programmed regimen with regard to higher likelihood of healthy live birth and lower risk of pregnancy loss and maternal hypertensive disorders of pregnancy.

Is artificial endometrial preparation more associated with early-onset or late-onset preeclampsia after frozen embryo transfer?

PURPOSE

To explore whether the risks of early- or late-onset preeclampsia vary among frozen embryo transfer (FET) with different regimens for endometrial preparation and fresh embryo transfer (FreET).

METHODS

We retrospectively included a total of 24129 women who achieved singleton delivery during their first cycles of in vitro fertilization (IVF) between January 2012 and March 2020. The risks of early- and late-onset preeclampsia after FET with endometrial preparation by natural ovulation cycles (FET-NC) or by artificial cycles (FET-AC) were compared to that after FreET.

RESULTS

After adjustment via multivariable logistic regression, the total risk of preeclampsia was higher in the FET-AC group compared to the FreET group [2.2% vs. 0.9%; adjusted odds ratio (aOR): 2.00; 95% confidence interval (CI): 1.45-2.76] and FET-NC group (2.2% vs. 0.9%; aOR: 2.17; 95% CI: 1.59-2.96).When stratified by the gestational age at delivery based on < 34 weeks or ≥ 34 weeks, the risk of late-onset preeclampsia remained higher in the FET-AC group than that in the and FreET group (1.8% vs. 0.6%; aOR: 2.56; 95% CI: 1.83-3.58) and the FET-NC group (1.8% vs. 0.6%; aOR: 2.63; 95% CI: 1.86-3.73). We did not find a statistically significant difference in the risk of early-onset preeclampsia among the three groups.

CONCLUSIONS

An artificial regimen for endometrial preparation was more associated with an increased risk of late-onset preeclampsia after FET. Given that FET-AC is widely used in clinical practice, the potential maternal risk factors for late-onset preeclampsia when using the FET-AC regimen should be further explored, considering the maternal origin of late-onset preeclampsia.

Diminished ovarian reserve may not be associated with a poorer fresh cycle outcome in women < 38 years

BACKGROUND

Previous studies have discussed the pregnancy outcomes of diminished ovarian reserve (DOR) patients. However, data on embryonic development potential, neonatal outcomes, and maternal complications of DOR patients still remained unknown. This is the first study to investigate the risk of DOR on pregnancy and perinatal outcomes among women < 38 years.

METHODS

Retrospective cohort study was conducted. Patients (< 38 years of age) undergoing their first oocyte retrieval cycle were included. Patients were divided into DOR group and non-DOR group. Pregnancy outcomes of fresh cycle and cumulative live birth rate and perinatal outcomes after one oocyte retrieved cycle were compared between DOR and non-DOR group.

RESULT(S)

From January 2016 to September 2020, there were 8,179 patients involved: 443 patients in the DOR group and 7,736 patients in the non-DOR group. The incidences of live birth and clinical pregnancy did not differ significantly between patients with or without DOR after fresh cycle transfer, but the cumulative live birth rate was significantly lower in DOR group. Among women who had singleton live births, after binary logistic regression, the rates of maternal complications and neonatal outcomes were comparable in the two groups.

CONCLUSION(S)

DOR patients (< 38 years of age) showed similar pregnancy outcomes in the first fresh embryo transfer cycle but a lower chance of live birth after a whole oocyte retrieval cycle to non-DOR patients and DOR is not associated with adverse perinatal outcomes.

Pregnancy and neonatal outcomes of letrozole versus natural cycle frozen embryo transfer of autologous euploid blastocyst

PURPOSE

To investigate the pregnancy and neonatal outcomes of letrozole-stimulated frozen embryo transfer (LTZ-FET) cycles compared with natural FET cycles (NC-FET).

METHODS

Our retrospective cohort included all LTZ-FET (n = 161) and NC-FET (n = 575) cycles that transferred a single euploid autologous blastocyst from 2016 to 2020 at Stanford Fertility Center. The LTZ-FET protocol entailed 5 mg of daily letrozole for 5 days starting on cycle day 2 or 3. Outcomes were compared using absolute standardized differences (ASD), in which a larger ASD signifies a larger difference. Multivariable regression models adjusted for confounders: maternal age, BMI, nulliparity, embryo grade, race, infertility diagnosis, and endometrial thickness.

RESULTS

The demographic and clinical characteristics were overall similar. A greater proportion of the letrozole cohort was multiparous, transferred high-graded embryos, and had ovulatory dysfunction. The cohorts had similar pregnancy rates (67.1% LTZ vs 62.1% NC; aOR 1.31, P = 0.21) and live birth rates (60.9% LTZ vs 58.6% NC; aOR 1.17, P = 0.46). LTZ-FET neonates on average were born 5.7 days earlier (P < 0.001) and had higher prevalence of prematurity (18.6% vs. 8.0%NC, ASD = 0.32) and low birth weight (10.4% vs. 5.0%, ASD = 0.20). Both cohorts' median gestational ages (38 weeks and 1 day for LTZ; 39 weeks and 0 day for NC) were full term.

CONCLUSION

There were similar rates of pregnancy and live birth between LTZ-FET and NC-FET cycles. However, there was a higher prevalence of prematurity and low birth weight among LTZ-FET neonates. Reassuringly, the median gestational age in both cohorts was full term, and while the difference in gestational length of almost 6 days does not appear to be clinically significant, this warrants larger studies.

The future of frozen-thawed embryo transfer in hormone replacement therapy cycles

PURPOSE OF REVIEW

This review focuses on the efficacy of letrozole stimulated frozen-thawed embryo transfer (FET) compared to hormone replacement therapy (HRT) FET in women with polycystic ovarian syndrome (PCOS) and/or oligo-anovulation. Further, obstetric and perinatal risks in HRT FET are summarized.

RECENT FINDINGS

The presence of a corpus luteum seems to reduce the risk of pregnancy-related hypertension and preeclampsia after FET. As a natural cycle (NC) FET is not an option for women with oligo-/amenorrhea these women may benefit from FET with mild stimulation compared to HRT FET. The intention of mild stimulation in anovulatory women is to induce (mono) ovulation to mimic the endocrine profiles of the natural cycle and the early pregnancy after natural conception. Mild stimulation by letrozole is patient friendly and cheap compared to gonadotropin stimulated FET and has been increasingly used in recent years. Although the quality of evidence is low, the pregnancy outcomes after letrozole FET seems similar or even better compared to HRT FET in women with PCOS and/or oligo-anovulation.

SUMMARY

Natural and modified NC FET should be used whenever possible to mitigate adverse obstetric and perinatal outcomes after HRT FET. For anovulatory women, whenever ovulation can be induced, we advocate the use of mild stimulation FET to create a corpus luteum awaiting results from RCTs limited to oligo-anovulatory women.

Hormone replacement cycles are associated with a higher risk of hypertensive disorders: Retrospective cohort study in singleton and twin pregnancies

OBJECTIVE

To elaborate the associations of different cycle regimens (natural cycle [NC], stimulated cycle [SC], hormone replacement cycle [HRC]) on maternal and neonatal adverse pregnancy outcomes after frozen-thawed embryo transfers (FET).

DESIGN

Population-based registry study.

SETTING

Swiss IVF Registry.

POPULATION OR SAMPLE

Singleton (n = 4636) and twin (n = 544) live births after NC-FET (n = 776), SC-FET (n = 758) or HRC-FET (n = 3646) registered from 2014 to 2019.

METHODS

Fifteen pregnancy pathologies were modelled for singleton and twin pregnancies using mixed models adjusted for cycle regimen, delivery, fertilisation technique, chronic anovulation, age of mother and centre.

MAIN OUTCOME MEASURES

Maternal (vaginal bleeding, isolated arterial hypertension and pre-eclampsia) and neonatal (gestational age, birthweight, mode of delivery) adverse pregnancy outcomes.

RESULTS

In singleton pregnancies, the incidences of bleeding in first trimester, isolated hypertension and pre-eclampsia were highest in HRC-FET with doubled odds of bleeding in first trimester (adjusted odds ratio [aOR] 2.23; 95% CI 1.33-3.75), isolated hypertension (aOR 2.50; 95% CI 1.02-6.12) and pre-eclampsia (aOR 2.16; 95% CI 1.13-4.12) in HRC-FET vs. NC-FET and with doubled respectively sixfold odds of bleeding (aOR 2.08; 95% CI 1.03-4.21) and pre-eclampsia (6.02; 95% CI 1.38-26.24) in HRC-FET versus SC-FET. In twin pregnancies, the incidence of pre-eclampsia was highest in HRC-FET with numerically higher odds of pre-eclampsia in HRC-FET versus NC-FET and versus SC-FET.

CONCLUSIONS

Our data implied the highest maternal risks of hypertensive disorders in HRC-FET, therefore clinicians should prefer SC-FET or NC-FET if medically possible.

Pre-eclampsia

Pre-eclampsia is a life-threatening disease of pregnancy unique to humans and a leading cause of maternal and neonatal morbidity and mortality. Women who survive pre-eclampsia have reduced life expectancy, with increased risks of stroke, cardiovascular disease and diabetes, while babies from a pre-eclamptic pregnancy have increased risks of preterm birth, perinatal death and neurodevelopmental disability and cardiovascular and metabolic disease later in life. Pre-eclampsia is a complex multisystem disease, diagnosed by sudden-onset hypertension (>20 weeks of gestation) and at least one other associated complication, including proteinuria, maternal organ dysfunction or uteroplacental dysfunction. Pre-eclampsia is found only when a placenta is or was recently present and is classified as preterm (delivery <37 weeks of gestation), term (delivery ≥37 weeks of gestation) and postpartum pre-eclampsia. The maternal syndrome of pre-eclampsia is driven by a dysfunctional placenta, which releases factors into maternal blood causing systemic inflammation and widespread maternal endothelial dysfunction. Available treatments target maternal hypertension and seizures, but the only 'cure' for pre-eclampsia is delivery of the dysfunctional placenta and baby, often prematurely. Despite decades of research, the aetiology of pre-eclampsia, particularly of term and postpartum pre-eclampsia, remains poorly defined. Significant advances have been made in the prediction and prevention of preterm pre-eclampsia, which is predicted in early pregnancy through combined screening and is prevented with daily low-dose aspirin, starting before 16 weeks of gestation. By contrast, the prediction of term and postpartum pre-eclampsia is limited and there are no preventive treatments. Future research must investigate the pathogenesis of pre-eclampsia, in particular of term and postpartum pre-eclampsia, and evaluate new prognostic tests and treatments in adequately powered clinical trials.

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.

Hormone replacement treatment regimen is associated with a higher risk of hypertensive disorders of pregnancy in women undergoing frozen-thawed embryo transfer

INTRODUCTION

In frozen-thawed embryo transfer (FET) cycles, hormone replacement treatment (HRT) was associated with a higher risk of hypertensive disorders of pregnancy (HDP) compared with natural cycles (NC). Multiple pregnancy was a risk factor for HDP and several studies did not conduct subgroup analysis of singleton pregnancy and multiple pregnancy.

OBJECTIVE

To investigate whether HRT regimen could be a risk factor for HDP in women undergoing FET cycles in singleton and twin pregnancies.

METHODS

A retrospective cohort study at a tertiary hospital, including a total of 9120 women who underwent FET and achieved ongoing pregnancy; 7590 patients underwent HRT-FET and 1530 NC-FET. The main outcome was HDP. HDP were analyzed for singleton and twin pregnancies, respectively.

RESULTS

In the singleton pregnancy, the risk of HDP in the HRT-FET group was significantly higher than that in the NC-FET group (6.21% vs. 4.09%; P=0.003). After adjusting for female age oocyte pick up, female age at FET and body mass index (BMI), HRT was found as a risk factor for HDP (adjusted odds ration [aOR]: 1.43; 95% confidence interval [CI]: 1.07 to 1.91; P=0.017). In the multiple pregnancy, the risk of HDP in the HRT-FET and NC-FET groups was similar.

CONCLUSION

HRT was associated with a higher risk of HDP in women who underwent FET and achieved singleton pregnancy.

Programmed frozen embryo transfer cycle increased risk of hypertensive disorders of pregnancy: a multicenter cohort study in ovulatory women

BACKGROUND

Although live birth rates were comparable between programmed and natural frozen-thawed embryo transfer cycles, recent data showed that pregnancies after programmed cycle were associated with an increased risk of adverse perinatal outcomes, such as hypertensive disorders of pregnancy. Such a difference might be attributed to selection bias because patients with ovulation disorders are more likely to receive programmed endometrial preparation protocol than natural cycle.

OBJECTIVE

This study aimed to analyze whether programmed endometrial preparation protocol is associated with an increased risk of adverse perinatal outcomes compared with natural cycle during frozen embryo transfer in ovulatory women.

STUDY DESIGN

This regional multicenter retrospective cohort study was conducted in 5 reproductive medical centers in Southeast China. Patients with regular cycles (21-35 days), who underwent either programmed or natural cycle blastocyst frozen embryo transfer and delivered singleton live birth babies after 28 weeks of gestation between 2016 and 2019 were analyzed. Each patient only contributed 1 cycle per cohort. The patients' frozen embryo transfer treatment cycles were linked to their obstetrical medication record, and a comprehensive medical record review was conducted to compare the maternal and neonatal outcomes between natural cycle and programmed cycle. Crude and adjusted odds ratios with 95% confidence intervals were calculated, and adjustment was made for relevant confounders.

RESULTS

Study samples included 499 natural cycle frozen embryo transfer cases and 900 programmed frozen embryo transfer cases. Pregnancies after programmed cycle were associated with increased odds of hypertensive disorders of pregnancy (adjusted odds ratio, 2.71; 95% confidence interval, 1.59-4.91) and preeclampsia (adjusted odds ratio, 2.71; 95% confidence interval, 1.17-6.23) compared with pregnancies after natural cycle. No significant difference was detected regarding other adverse perinatal outcomes between the 2 endometrial protocols. In subgroup analysis, both the subgroups of hormone replacement therapy and hormone replacement therapy with gonadotrophin-releasing hormone analogue pretreatment had increased odds of developing hypertensive disorders of pregnancy than the natural cycle group. The risk of developing preeclampsia was higher in the hormone replacement therapy with gonadotrophin-releasing hormone analogue pretreatment subgroup than in the other 2 groups (adjusted odds ratio, 4.99; 95% confidence interval, 1.94-12.82) (aOR, 2.47; 95% CI, 1.17-5.18).

CONCLUSION

Pregnancies after programmed frozen embryo transfer were associated with higher risks of hypertensive disorders of pregnancy in ovulatory women. The hormone replacement therapy with gonadotrophin-releasing hormone analogue pretreatment cycle led to the highest risk of preeclampsia among the 3 protocols.

Letrozole-induced endometrial preparation improved the pregnancy outcomes after frozen blastocyst transfer compared to the natural cycle: a retrospective cohort study

Background

Letrozole treatment is considered an effective option in endometrial preparation for frozen embryo transfers in patients with ovulation disorders or irregular menstruation; however, the effectiveness of letrozole-induced endometrial preparation remains unclear in ovulatory patients. Furthermore, there is no comparative study reporting on pregnancy complications and congenital anomalies after frozen embryo transfers comparing natural and letrozole-assisted cycles. This study examined whether letrozole-induced endometrial preparation affected pregnancy outcomes, perinatal outcomes, and congenital anomalies after single vitrified-warmed blastocyst transfers (SVBTs) in ovulatory patients, as compared with the natural cycle.

Methods

This historic cohort study included only patients with unexplained infertility. Overall, 14,611 patients who underwent SVBTs between July 2015 and June 2020, comprising both natural and letrozole-assisted cycles, were included. Multiple covariates that impact outcomes were used for propensity score matching; 1,911 patients in the letrozole group were matched to 12,700 patients in the natural group, and the clinical records of 1,910 patients in each group were retrospectively analysed. Cycle characteristics, pregnancy outcomes (clinical pregnancy, ongoing pregnancy, and live birth), and incidence of pregnancy complications and congenital anomalies were statistically compared between the two groups.

Results

Multivariate logistic regression analysis showed that letrozole administration during SVBT cycles significantly improved the live birth rate (P = 0.0355). Gestational age, birth length, birth weight, and infant sex, as well as the incidence of pregnancy complications and birth defects, were statistically comparable between the two groups. Furthermore, multivariate logistic regression analysis revealed that the perinatal outcomes were not affected by letrozole-induced endometrial preparation.

Conclusions

Letrozole-induced endometrial preparation improved the live birth rate compared with the natural cycle, without adverse effects on perinatal outcomes and congenital anomalies after SVBTs. Therefore, letrozole-induced endometrial preparation might be a safe and more effective strategy, especially for patients with insufficient luteal function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05174-0.

Association between programmed frozen embryo transfer and hypertensive disorders of pregnancy

Dissociation of embryo transfer from the ovarian stimulation cycle has afforded patients increased flexibility for genetic testing and fertility preservation. Although frozen embryo transfer (FET) has largely been demonstrated to be safe and effective compared with fresh transfer, programmed FET cycles, where a corpus luteum is absent, have come under increasing scrutiny. In observational trials, programmed FET protocols appear to be associated with an increased risk of ineffective decidualization and impaired placental function. Together with the appropriate preexisting risk factors, this additive risk may potentiate hypertensive disorders of pregnancy later in gestation. Efforts to understand the reasons for this apparent risk may afford us opportunities to better individualize the FET cycle type offered to patients with cryopreserved embryos. Randomized controlled trials will help us to understand whether the apparent risk is due to patient factors, which influence protocol choice, or a characteristic of the protocol itself, such as the absence of the corpus luteum or suboptimal replacement of estradiol and progesterone.

Impact of different endometrial preparation protocols before frozen embryo transfer on pregnancy outcomes: a review

The use of frozen embryo transfer cycles has exponentially increased in the last few years. Optimization of endometrial preparation protocols before frozen embryo transfer is mandatory to further improve pregnancy outcomes. This review will focus on the existing literature with regard to the different available endometrial preparation protocols and their impact on pregnancy outcomes. More specifically, we will focus on programmed, natural, and stimulated frozen embryo transfer cycles. The studies performed on this topic are generally of low quality, and only a few well-performed randomized controlled trials have been published. To date, no strong evidence is available to support the use of 1 preparation method over another in terms of pregnancy outcomes. However, robust data have shown a clearly protective effect of natural frozen embryo transfer cycles against long-term obstetric complications, mainly hypertensive disorders of pregnancy and large for gestational age infants. The introduction of individualized luteal phase support in different endometrial preparation protocols is actually gaining a lot of attention and requires further investigation.

Endometrial thickness is an independent risk factor of hypertensive disorders of pregnancy: a retrospective study of 13,458 patients in frozen-thawed embryo transfers

BACKGROUND

Hypertensive disorders of pregnancy (HDP) are an important cause of maternal and fetal mortality, and its potential risk factors are still being explored. Endometrial thickness (EMT), as one of the important monitoring indicators of endometrial receptivity, has been confirmed to be related to the incidence of HDP in fresh embryo transfer. Our study was designed to investigate whether endometrial thickness is associated with the risk of hypertensive disorders of pregnancy in frozen-thawed embryo transfer (FET).

METHODS

This respective cohort study enrolled 13,458 women who received vitrified embryo transfer and had a singleton delivery in the Reproductive Hospital affiliated to Shandong University from January 2015 to December 2019. We set strict screening criteria and obtained the information from the hospital electronic medical system. Statistical methods including logistic regression analysis, receiver operating characteristic curve and restricted cubic spline were used to evaluate the relationship between endometrial thickness and the incidence of pregnancy-induced hypertension.

RESULTS

The incidences of HDP in a thin endometrial thickness group (< 0.8 cm) and a thick endometrial thickness group (> 1.2 cm) were significantly greater than in a reference group (0.8 cm-1.2 cm) (7.98 and 5.24% vs 4.59%, P <  0.001). A nonlinear relationship between endometrial thickness and risk of hypertensive disorders of pregnancy was examined by restricted cubic spline (P <  0.001). The thin endometrial thickness and thick endometrial thickness groups were significantly associated with the risk of HDP after adjusting for confounding variables by stepwise logistic regression analysis. Subsequently, subgroup logistic regression analysis based on endometrial preparation regimens showed that thin endometria were still significantly associated with a higher morbidity rate in the artificial cycle group, while in the natural cycle group, thick endometria were closely associated with increased morbidity.

CONCLUSION

Our study manifested that both the thin and thick endometria were associated with an increased risk of hypertensive disorders of pregnancy in frozen embryo transfer cycles. Reproductive clinicians should focus on adjusting endometrial thickness in different preparation regimens; and obstetricians should be mindful of the risk of hypertension during pregnancy, when women with thin (< 0.8 cm) or excessively thicker (> 1.2 cm) endometrial thickness achieve pregnancy through frozen-thawed embryo transfer.

Analysis of the risk of complications during pregnancy in pregnant women with assisted reproductive technology: a retrospective study using registry linkage from 2013 to 2018 in Shanghai, China

Background

To evaluate the differences in pregnancy outcomes between assisted reproductive technology (ART) patients and natural pregnant women in Shanghai, China in the past 6 years objectively. And to assess the feasibility of the research method of registry-database linkage in mainland China.

Methods

This retrospective study was conducted using registry-database linkage. A total of 8102 pregnancies with ART and 8096 parturients with spontaneous conception (SC) from 10 reproductive centers and 111 hospitals composed our retrospective study. The primary outcomes were the rates of obstetric complications (pregnancy-induced hypertention [PIH], gestational diabetes mellitus [GDM], placenta previa, mode of delivery, preterm birth [PTB], low birth weight [LBW], and macrosomia). The prenatal outcomes were compared between ART and SC parturients, frozen-thawed embryo transfer (FET) and fresh embryo transfer, and in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). We calculated odds ratios (ORs) and 95% confidence intervals (CIs).

Results

The final matching rate of the target population was 92% by using registry linkage. ART resulted in a higher rate of multiple birth, PTB, LBW, cesarean section, placenta previa and GDM compared with SC in the singleton cohort. In ART patients, pregnant women with FET had a significantly higher risk of PIH than those with fresh embryo transfer (14.1% Vs 9.3%, AOR1.528, 95% CI 1.303–1.793), but there was no difference between IVF and ICSI. FET is also related to the severity of PIH.

Conclusions

ART increased the rate of complications during pregnancy, the risk and severity of PIH in patients with FET was higher than that in patients with fresh embryo transfer. The registry-database linkage study is an objective and feasible research method in mainland China.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04846-1.

Should any use of artificial cycle regimen for frozen-thawed embryo transfer in women capable of ovulation be abandoned: yes, but what's next for FET cycle practice and research?

Over the past decade, the use of frozen-thawed embryo transfer (FET) treatment cycles has increased substantially. The artificial ('programmed') cycle regimen, which suppresses ovulation, is widely used for that purpose, also in ovulatory women or women capable of ovulation, under the assumption of equivalent efficacy in terms of pregnancy achievement as compared to a natural cycle or modified natural cycle. The advantage of the artificial cycle is the easy alignment of the time point of thawing and transferring embryos with organizational necessities of the IVF laboratory, the treating doctors and the patient. However, recent data indicate that pregnancy establishment under absence of a corpus luteum as a consequence of anovulation may cause relevant maternal and fetal risks. Herein, we argue that randomized controlled trials (RCTs) are not needed to aid in the clinical decision for or against routine artificial cycle regimen use in ovulatory women. We also argue that RCTs are unlikely to answer the most burning questions of interest in that context, mostly because of lack of power and precision in detecting rare but decisive adverse outcomes (e.g. pre-eclampsia risk or long-term neonatal health outcomes). We pinpoint that, instead, large-scale observational data are better suited for that purpose. Eventually, we propose that the existing understanding and evidence is sufficient already to discourage the use of artificial cycle regimens for FET in ovulatory women or women capable of ovulation, as these may cause a strong deviation from physiology, thereby putting patient and fetus at avoidable health risk, without any apparent health benefit.

Potential role of the corpus luteum in maternal cardiovascular adaptation to pregnancy and preeclampsia risk

Studies in the gravid rat model revealed a key role for the corpus luteal hormone, relaxin, in the maternal circulatory changes of early pregnancy epitomized by profound systemic vasodilation and increased arterial compliance. To determine whether the corpus luteum may play a similar role in human pregnancy, women who conceived by in vitro fertilization were studied. Implementation of artificial (programmed) cycles for embryo transfers, which precluded the formation of a corpus luteum, was associated with notable attenuation of the gestational rise in cardiac output and fall in carotid-femoral pulse wave velocity (reflecting impairment of arterial dilation and increased compliance, respectively) and deficiencies in other cardiovascular changes normally observed during the first trimester. Cardiac output and carotid-femoral pulse wave velocity were restored after the first trimester of pregnancy, consistent with rescue by placental vasodilators, such as placental growth factor. In addition, a potential role of corpus luteal factors in reducing the risk of developing preeclampsia was hypothesized. In most single and multiple center, prospective and retrospective cohort (and registry) studies, the risk of developing preeclampsia and preeclampsia with severe features was increased specifically in women undergoing autologous frozen embryo transfer in artificial cycles without the formation of a corpus luteum relative to natural, modified natural, stimulated, or controlled ovarian stimulation cycles and spontaneous pregnancies-all associated with the formation of at least 1 corpus luteum. Taken together, these observational studies are sufficiently compelling to warrant randomized clinical trials comparing preeclampsia risk in autologous frozen embryo transfer in natural vs artificial cycles. Impaired endometrial function because of suboptimal hormonal administration is an alternative but not mutually exclusive explanation for increased preeclampsia risk in autologous frozen embryo transfer in artificial cycles. Potential mechanisms by which the corpus luteum may reduce the risk of developing preeclampsia and whether autologous frozen embryo transfer in artificial cycles is associated with increased risk of preterm preeclampsia, term preeclampsia, or both are discussed. Last, suggestions for future investigations are noted.

Treatment outcomes of blastocysts thaw cycles, comparing the presence and absence of a corpus luteum: a systematic review and meta-analysis

PURPOSE

This study aims to review the literature and perform a meta-analysis to determine if the presence of a corpus luteum has an impact on treatment outcomes in thaw cycles, where blastocyst embryos are transferred.

METHOD

PUBMED, EMBASE, CENTRAL and CINAHL were searched for papers published between January 2017 and 27 July 2020. Additional articles were selected from the reference list of the results and previous reviews. Three reviewers independently reviewed and extracted data. The meta-analysis was conducted though RevMan V.5.4.1. Studies were quality assessed with the Cochrane risk of bias tool and the Newcastle-Ottawa Scale.

RESULTS

Nine publications were included for data extraction and subsequent meta-analysis. Two studies were randomised controlled trials, and seven were cohort studies. Subgroup analysis of the different study designs was performed. While the rates of positive human chorionic gonadotropin results (relative risk, RR 1.0, 95% CI 0.95 to 1.05) and clinical pregnancies (RR 1.06, 95% CI 0.96 to 1.18) were comparable between the two groups, the rates of live births were higher in thaw cycles with a corpus luteum (RR 1.14, 95% CI 1.06 to 1.22). Analysis of pregnancy losses demonstrated that both biochemical pregnancy (early miscarriage) (RR 0.71, 95% CI 0.62 to 0.82) and miscarriages (RR 0.72, 95% CI 0.62 to 0.83) were increased in cycles without a corpus luteum.

CONCLUSION

Where clinically appropriate, the use of cycle types that have a functional corpus luteum should be favoured. There were several limitations to this study, including the quality of studies and the inherent bias of retrospective cohort studies. Further, high-quality research, particularly randomised controlled trials with blastocysts embryos, is required to further explore these findings.

PROSPERO REGISTRATION NUMBER

CRD42020209583.

Preconception ovarian reserve and placenta-mediated pregnancy complications among infertile women

RESEARCH QUESTION

Are preconception ovarian reserve markers, such as Anti-Mullerian hormone and antral follicle count, associated with preeclampsia and placenta mediated pregnancy complications among women with unexplained infertility who conceive with superovulation?

DESIGN

This is a secondary analysis of women with unexplained infertility who had a singleton live birth after enrollment in the Analysis of Multiple Intrauterine Gestations after Ovarian Stimulation (AMIGOS) trial that randomized couples to superovulation with letrozole, clomiphene, or gonadotropins with insemination for up to 4 cycles.

RESULTS

Compared to controls (N = 156), women who developed preeclampsia (N = 17) had lower Anti-Mullerian hormone levels (2.24 ± 1.20 vs. 2.89 ± 2.32, p = 0.07) and lower antral follicle count (18 ± 7.67 vs. 21 ± 11.43, p = 0.16); though these differences were not statistically significant. There was no relationship between Anti-Mullerian hormone (OR: 1.00, 95% CI: 0.76-1.25) or antral follicle count (OR: 0.98, 95% CI 0.93-1.04) with preeclampsia and between Anti-Mullerian hormone (OR: 1.00, 95% CI: 0.83-1.17) and antral follicle count (OR: 1.00, 95% CI: 0.97-1.04) with placenta medicated pregnancy complications after adjusting for age, BMI and race.

CONCLUSIONS

Preconception ovarian reserve markers are not associated with preeclampsia and placenta mediated pregnancy complications among women with unexplained infertility who conceive with superovulation with insemination.

Endometrial preparation does not affect the risk of hypertensive disorders of pregnancy in low-risk women undergoing frozen embryo transfer

OBJECTIVE

Frozen embryo transfer (FET) is associated with a higher risk of hypertensive disorders in pregnancy. The objective of the present study is to evaluate the effect of different protocols of endometrial preparation on the risk of these disorders.

METHODS

We conducted a retrospective cohort study on 594 singleton pregnancies achieved by embryo transfer of single frozen-thawed blastocysts. Women with preexisting risk factors for hypertensive disorders were excluded. Women were divided into two groups according to the endometrial preparation protocol: either natural cycle (n = 495) or programming cycle with hormonal replacement therapy (n = 97). The primary outcome was the frequency of hypertensive disorders in pregnancy: specifically, gestational hypertension and preeclampsia.

RESULTS

No differences emerged between women following the natural cycle and those following the programming cycle in the frequency of gestational hypertension (5 vs. 4%) and preeclampsia (1.1 vs. 1.2%). No impact emerged also after multivariate analyses.

CONCLUSIONS

Women receiving hormonal replacement therapy have the same risk of gestational hypertension and preeclampsia as women following natural cycles when considering low-risk singleton pregnancies.

The impact of endometrial preparation for frozen embryo transfer on maternal and neonatal outcomes: a review

The use of frozen embryo transfer in assisted reproductive technology (ART) has steadily increased since development in the early 1980's. While there are many benefits to delayed frozen embryo transfer, certain adverse perinatal outcomes are noted to be more common in these transfers when compared to fresh transfers, specifically hypertensive disorders of pregnancy. Frozen embryo transfers require coordination between the embryo's developmental stage and the endometrial environment and can occur in either ovulatory or programmed cycles. Though there is no consensus on the ideal method of endometrial preparation prior to frozen embryo transfer, emerging data suggests differences in maternal and neonatal outcomes, specifically increased rates of hypertensive disorders of pregnancy in programmed cycles. Other reported differences include an increased risk of cesarean delivery, placenta accreta, postpartum hemorrhage, low birthweight, preterm birth, post term delivery, macrosomia, large for gestational age, and premature rupture of membranes in programmed cycles. The mechanism by which these differences exist could reflect inherent differences in groups selected for each type of endometrial preparation, the role of super physiologic hormone environments in programmed cycles, or the unique contributions of the corpus luteum in ovulatory cycles that are not present in programmed cycles. Given that existing studies are largely retrospective and have several key limitations, further investigation is needed. Confirmation of these findings has implications for current practice patterns and could enhance understanding of the mechanisms behind important adverse perinatal outcomes in those pursuing assisted reproduction.

Natural cycle increases the live-birth rate compared with hormone replacement treatment for frozen-thawed single euploid blastocyst transfer

BACKGROUND

A number of studies have compared the clinical outcomes between the two endometrial preparation methods: natural cycles (NCs) and hormone replacement treatment (HRT) before frozen embryo transfer, but the results were conflicting. In order to mitigate the potential effect of embryos per se, several researchers have worked on this subject for euploid blastocyst transfer, but the results were still inconsistent. Therefore, the present study was aimed to investigate the clinical outcomes between HRT and NC for autologous single vitrified-warmed euploid blastocyst transfer based on our data.

METHODS

A total of 598 frozen-thawed single euploid blastocyst transfer cycles in the assisted reproductive center of Northwest Women's and Children's Hospital from January 2014 to May 2021 were retrospectively analyzed. Women were stratified into the NC (n = 125) or HRT (n = 473) group according to the patient's preference and the physician's guidance. Multivariate regression models and subgroup analysis were constructed to analyze the association between endometrial preparation and live birth.

RESULTS

Women in the NC group had a higher live birth rate (68.80% versus 58.35%, P = 0.034) and a lower risk of total pregnancy loss (8.51% versus 21.14%, P = 0.005) when compared with women in the HRT group. The biochemical pregnancy rate (75.20% versus 74.00%, P = 0.784) and clinical pregnancy rate (74.40% versus 69.98%, P = 0.334) were similar between the two groups (NC versus HRT). NC was associated with an increased odds of live birth compared with HRT by different multivariable analysis models (Model 1: adjusted odds ratio [aOR], 95% confidence interval [CI]: 0.57, 0.36 - 0.90; Model 2: aOR, 95%CI: 0.57, 0.35 - 0.92). In addition, the increased chance of live birth in the NC group was found in all subgroups. No major obstetrical complications and two malformation livebirths were reported.

CONCLUSIONS

In women undergoing single euploid frozen blastocyst transfers, the NC group was associated with a lower pregnancy loss rate and an ultimately higher live birth rate than the HRT group. Although HRT is convenient for both clinicians and patients, the lower live birth rate should be taken into account and NC might be the first choice of endometrial preparation method.

Comparison of Perinatal Outcomes of Letrozole-Induced Ovulation and Hormone Replacement Therapy Protocols in Patients With Abnormal Ovulation Undergoing Frozen-Thawed Embryo Transfer: A Propensity Score Matching Analysis

BACKGROUND

With the increasing use of frozen embryo transfer (FET), the best endometrial preparation protocol is continuously being discussed. The hormone replacement therapy (HRT) cycle and letrozole-induced ovulation (L-OI) cycle are available protocols for patients with abnormal ovulation. Previous comparisons of the two protocols have focused on pregnancy outcomes, with less attention to perinatal outcomes, and population heterogeneity was large; thus, convincing conclusions about which protocol is more appropriate could not be drawn.

METHODS

We performed a retrospective cohort study using propensity score matching (PSM) analysis for a population of patients undergoing FET cycles in the reproductive center of the Third Affiliated Hospital of Zhengzhou University from January 2016 to September 2020. The main outcome measures were clinical pregnancy rate, live birth rate, very preterm delivery (VPTD), preterm delivery (PTD), low birth weight (LBW), macrosomia, small for gestational age (SGA), large for gestational age (LGA), hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM), premature rupture of membranes (PROM), placenta previa, and congenital abnormality.

RESULTS

A total of 8010 women were enrolled. Due to the large heterogeneity among the patients, we conducted 1:1 PSM, and 1461 women matched in each group. Compared with the HRT group, the L-OI group had a smaller proportion of thin endometrium (27.38% vs. 41.07%) and thicker endometrium on the day of embryo transfer (9.63 ± 1.82 vs. 8.91 ± 1.38). There were no significant differences in clinical pregnancy rate, early abortion rate or live birth rate between the groups. There was no significant difference in perinatal outcomes of singleton live birth, including VPTD, PTD, postterm delivery, LBW, macrosomia, SGA, LGA, GDM, HDP, placenta previa, and congenital malformation.

CONCLUSION

For women with abnormal ovulation, the pregnancy and perinatal outcomes of HRT and L-OI protocols are reassuring. It seems that both protocols are safe and effective for endometrial preparation in frozen-thawed embryo transfer in the clinic.

Protective placental inflammatory and oxidative stress responses are attenuated in the context of twin pregnancy and chorioamnionitis in assisted reproduction

PURPOSE

Assisted reproduction technologies (ART) are associated with increased risks of pregnancy complications and obstetric interventions. Here, we aimed to determine if ART affects placental inflammation and oxidative stress as a mechanism for unfavorable pregnancy outcomes.

METHODS

The levels of six cytokines (IFN-γ, IL-1β, IL-6, IL-8, IL-10, TNFα) were measured using multiplex ELISA. The activity of four antioxidant enzymes (glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase, superoxide dismutase) and levels of two antioxidants (GSH, vitamin E) were measured using commercial/in-house assays. Markers were compared between ART and unassisted pregnancies, and then groups were stratified using ICD9/10 codes to determine differences in specific clinical contexts.

RESULTS

In unassisted twin pregnancies, there was a trend of decreased cytokine levels (IL-1β, IL-6, IL-8, TNFα, p < 0.05), but cytokines in ART twins were the same or higher. Additionally, GST and GPx activities were lower in unassisted twins, and vitamin E levels were higher in ART twins (p < 0.05). In pregnancies complicated by chorioamnionitis, there was a trend of increased cytokine levels in unassisted pregnancies (IL-1β, IL-6, and IL-8, p < 0.05). No increase was observed in ART, and IFN-γ and TNFα were decreased (p < 0.05). Placental GST and GPx activities were higher in unassisted pregnancies with chorioamnionitis compared to ART (p < 0.05).

CONCLUSION

Attenuation of protective placental inflammatory and oxidative stress responses may play a role in the underlying pathogenesis of negative birth outcomes in ART, expanding our understanding of adverse pregnancy outcomes when ART is used to conceive.

Corpus luteum number and the maternal renin-angiotensin-aldosterone system as determinants of utero-placental (vascular) development: the Rotterdam Periconceptional Cohort

BACKGROUND

Pregnancies with > 1 corpus luteum (CL) display a hyperdynamic circulation and an increased risk of small-for-gestational age deliveries. Among the factors released by the CL is prorenin, the inactive precursor of renin. Since the renin-angiotensin-aldosterone system (RAAS) is involved in early hemodynamic pregnancy adaptation, we linked both CL number and first-trimester concentrations of prorenin (as an indicator of RAAS activity) and the aldosterone/renin ratio (as an indicator of angiotensin-independent aldosterone effectiveness) to non-invasive markers of utero-placental (vascular) development, measured longitudinally from the first trimester onwards.

METHODS

A total of 201 women, who conceived naturally or after in-vitro fertilization treatment (with 0 (n = 8), 1 (n = 143), or > 1 (n = 51) CL), were selected from the Rotterdam Periconceptional Cohort. Maternal RAAS components were determined at 11 weeks gestation. Placental volume and utero-placental vascular volume were measured from transvaginal 3D ultrasound scans at 7, 9 and 11 weeks gestation, pulsatility and resistance indices of the uterine arteries were assessed by pulsed wave Doppler ultrasounds at 7, 9, 11, 13, 22 and 32 weeks gestation. At birth placental weight was obtained using standardized procedures.

RESULTS

Pregnancies without a CL show lower uterine artery indices throughout gestation than 1 CL and > 1 CL pregnancies, while parameters of placental development are comparable among the CL groups. After adjustment for patient- and treatment-related factors, first-trimester prorenin concentrations are positively associated with uterine artery pulsatility and resistance indices (β 0.06, 95% CI 0.01;0.12, p = 0.04 and β 0.10, 95% CI 0.01;0.20, p = 0.04, respectively), while high prorenin concentrations are negatively associated with first-trimester utero-placental vascular volume (β -0.23, 95% CI -0.44;-0.02, p = 0.04) and placental weight (β -93.8, 95%CI -160.3;-27.4, p = 0.006). In contrast, the aldosterone/renin ratio is positively associated with first-trimester placental volume (β 0.12, 95% CI 0.01;0.24, p = 0.04).

CONCLUSIONS

The absence of a CL, resulting in low prorenin concentrations, associates with low uterine artery pulsatility and resistance, while high prorenin concentrations associate with a low utero-placental vascular volume and weight. These data support a scenario in which excess prorenin, by upregulating angiotensin II, increases uterine resistance, thereby preventing normal placental (vascular) development, and increasing the risk of small-for-gestational age deliveries. Simultaneously, high aldosterone concentrations, by ensuring volume expansion, exert the opposite.

Pregnancy Outcomes After Frozen-Thawed Embryo Transfer in the Absence of a Corpus Luteum

Background: Nowadays, frozen-thawed embryo transfer (FET) cycles represent a high proportion of fertility treatments worldwide. Recent studies suggest differences in pregnancy outcomes depending on the FET treatment protocol used. The reason for this is still unclear, but the number of corpora lutea (CL) at conception is discussed as a possible factor. This study aims to investigate whether maternal and neonatal outcomes for pregnancies following FET lacking a CL differ from FET with one or more CL in order to explore a potential link between CL absence and adverse pregnancy outcomes.

Methods: The study was designed as a retrospective, multi-center observational study with two cohorts after singleton live birth [0 CL cohort (FET in a programmed cycle, n = 114) and ≥ 1 CL cohort (FET in a natural or stimulated cycle, n = 68)]. Participants completed a questionnaire on the outcome of pregnancy and birth records were analyzed in a descriptive way. Multivariable logistic and linear regressions were performed in order to explore associations between CL absence and pregnancy outcomes. The strength of the agreement between the information in the survey and the diagnoses extracted from the files was assessed by Cohen's Kappa.

Results: The risk of hypertensive disorders of pregnancy was higher after FET in the absence of a CL compared to FET with CL presence (aOR 5.56, 95% CI 1.12 – 27.72). Birthweights and birthweight percentiles were significantly higher in the 0 CL group. CL absence was a predictor of higher birthweight (adjusted coefficient B 179.74, 95% CI 13.03 – 346.44) and higher birthweight percentiles (adjusted coefficient B 10.23, 95%, 95% CI 2.28 – 18.40) particularly in female newborns of the 0 CL cohort. While the strength of the agreement between the reported information in the survey and the actual diagnoses extracted from the files was good for the majority of outcomes of interest it was fair in terms of hypertension (κ = 0.38).

Conclusion: This study supports observations suggesting a potential link between a lack of CL at conception and adverse maternal and neonatal outcomes. Further investigations on causes and pathophysiological relationships are yet to be conducted.

Natural vs. programmed cycles for frozen embryo transfer: study protocol for an investigator-initiated, randomized, controlled, multicenter clinical trial

Background

Randomized trials of assisted reproductive technology (ART) have been designed for outcomes of clinical pregnancy or live birth and have not been powered for obstetric outcomes such as preeclampsia, critical for maternal and fetal health. ART increasingly involves frozen embryo transfer (FET). Although there are advantages of FET, multiple studies have shown that risk of preeclampsia is increased with FET compared with fresh embryo transfer, and the reason for this difference is not clear. NatPro will compare the proportion of preeclampsia between two commonly used protocols for FET,modified natural and programmed cycle.

Methods

In this two-arm, parallel-group, multi-center randomized trial, NatPro will randomize 788 women to either modified natural or programmed FET and follow them for up to three FET cycles. Primary outcome will be the proportion of preeclampsia in women with a viable pregnancy assigned to a modified natural cycle FET (corpus luteum present) protocol compared to the proportion of preeclampsia in pregnant women assigned to a programmed FET (corpus luteum absent) protocol. Secondary outcomes will compare the proportion of live births and the proportion of preeclampsia with severe features between the protocols.

Conclusion

This study has a potential significant impact on millions of women who pursue ART to build their families. NatPro is designed to provide clinically relevant guidance to inform patients and clinicians regarding maternal risk with programmed and modified natural cycle FET protocols. This study will also provide accurate point estimates regarding the likelihood of live birth with programmed and modified natural cycle FET.

Trial registration

ClinicalTrials.govNCT04551807. Registered on September 16, 2020

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05637-3.