Difference in birth weight of consecutive sibling singletons is not found in oocyte donation when comparing fresh versus frozen embryo replacements

Egg donation and gestational surrogacy: Pregnancy is riskier with an unrelated embryo

Modern medicine has revolutionized family planning. Remarkably, women1 can carry to term embryos with whom they share no genetic connection, a feat made possible through egg donation and/or gestational surrogacy. Our reproductive systems evolved to accommodate embryos that are 50% related to the carrier, not 0% related. Here, we apply evolutionary theory to explain how and why pregnancy is riskier with an unrelated embryo. When a woman gestates an unrelated embryo, she is significantly more likely to develop preeclampsia and other diseases above and beyond the known risks associated with advanced maternal age, IVF, multiple gestation, and subfertility. Such "allogeneic pregnancies" are riskier even in fertile, healthy, commercial surrogates and when the egg is donated by a young, healthy donor. We propose that unrelated embryos present a special immune challenge to the gestational carrier, because they have fewer matching genes to the maternal body-therefore exacerbating symptoms of evolutionary maternal-fetal conflict. Indeed, maternal risks seem lower when the embryo is more related to the carrier, e.g., if a sister donates the egg. Finally, we discuss microchimerism in egg donation pregnancies, whereby wholly foreign cells pass from mother to embryo and vice-versa. We conclude with several medical proposals. First, egg donors and surrogates should be informed of the increased health risks they would face. In considerations of risk, these young, fertile women should not be compared to older, infertile women undergoing IVF; the proper comparison group is other young, fertile women. Second, contrary to some medical advice, perhaps genetically-related egg donors and surrogates should be preferred, all else equal. An immunological matching scheme, like what is used for organ transplants, could improve surrogate pregnancy outcomes. Third, more research is needed on microchimerism, sperm exposure, and the long-term impacts of allogeneic pregnancies on maternal and child health.

Perinatal outcomes in 6640 singleton pregnancies after donor oocyte IVF across three continents over 7 years

PURPOSE

Are trends in singleton donor oocyte IVF perinatal outcomes consistent over time among four international ethnically diverse infertility centers?

METHODS

This retrospective cohort consisted of an infertility network of four international IVF centers across three continents. Singleton live births resulting from fresh and frozen donor oocyte embryo transfers from January 1, 2012 to December 31, 2018 were included. The main outcome measures were birth weight (BW), preterm birth (PTB), large for gestational age (LGA), small for gestational age (SGA) and gestational age (GA) at delivery.

RESULTS

The entire cohort (n = 6640) consisted of 4753 fresh and 1887 frozen donor oocyte embryo transfers. Maternal age, parity, body mass index, neonatal sex and GA at delivery were similar for fresh and frozen donor oocyte embryo transfers in the entire cohort and within each infertility center. All four centers had a trend of decreased BW and rates of PTB before 32 weeks annually, although significance was not reached. Three of the four centers had annual increased trends of PTB before 37 weeks and LGA newborns, although significance was not reached. BWs for the entire cohort for fresh and frozen donor embryo transfers were 3166 g ± 601 g and 3137 g ± 626 g, respectively.

CONCLUSION

Similar trends in perinatal outcomes were present across four international infertility centers over 7 years. The overall perinatal trends in donor oocyte IVF may be applicable to centers worldwide, but further studies in more geographic regions are needed.

Elevated Sperm DNA Damage in IVF-ICSI Treatments Is Not Related to Pregnancy Complications and Adverse Neonatal Outcomes

This multicenter retrospective cohort study assesses the effect of high paternal DNA fragmentation on the well-being of the woman during pregnancy and the health of the newborn delivered. It was performed with clinical data from 488 couples who had a delivery of at least one newborn between January 2000 and March 2019 (243 used autologous oocytes and 245 utilized donated oocytes). Couples were categorized according to sperm DNA fragmentation (SDF) level as ≤15% or >15%, measured by TUNEL assay. Pregnancy, delivery, and neonatal outcomes were assessed. In singleton pregnancies from autologous cycles, a higher but non-significant incidence of pre-eclampsia, threatened preterm labor, and premature rupture of membranes was found in pregnant women from the >15%SDF group. Additionally, a higher proportion of children were born with low birth weight, although the difference was not statistically significant. After adjusting for potential confounders, these couples had lower odds of having a female neonate (AOR = 0.35 (0.1-0.9), p = 0.04). Regarding couples using donor's oocytes, pregnancy and neonatal outcomes were comparable between groups, although the incidence of induced vaginal labor was significantly higher in the >15% SDF group (OR = 7.4 (1.2-46.7), p = 0.02). Adjusted analysis revealed no significant association of elevated SDF with adverse events. In multiple deliveries from cycles using both types of oocytes, the obstetric and neonatal outcomes were found to be similar between groups. In conclusion, the presence of an elevated SDF does not contribute to the occurrence of clinically relevant adverse maternal events during pregnancies, nor does it increase the risk of worse neonatal outcomes in newborns. Nevertheless, a higher SDF seems to be related to a higher ratio of male livebirths.

Fetal Growth Velocity according to the Mode of Assisted Conception

INTRODUCTION

Pregnancies conceived through assisted reproductive techniques (ARTs) are on the rise worldwide and have been associated with a higher risk of placental-related disease in the third trimester.

METHODS

A cohort was created of singleton pregnancies after assisted reproduction, admitted at our institution for delivery, between January 2020 and August 2022. Fetal growth velocity from the second trimester to delivery was compared against a gestational-age-matched group of pregnancies spontaneously conceived according to the origin of the selected oocyte (i.e., autologous vs. donated).

RESULTS

125 singleton pregnancies conceived through ART were compared to 315 singleton spontaneous conceptions. Overall, after adjusting for possible confounders, multivariate analysis demonstrated that ART pregnancies had a significantly lower estimated fetal weight (EFW) z-velocity from the second trimester to delivery (adjusted mean difference = -0.002; p = 0.035) and a higher frequency of EFW z-velocity in the lowest decile (adjusted OR = 2.32 [95% CI, 1.15-4.68]). Also, when ART pregnancies were compared according to the type of oocyte, those conceived with donated oocytes showed a significantly lower EFW z-velocity from the second trimester to delivery (adjusted mean difference = -0.008; p = 0.001) and a higher frequency of EFW z-velocity in the lowest decile (adjusted OR = 5.33 [95% CI, 1.34-21.5]).

CONCLUSIONS

Pregnancies achieved through ART exhibit a pattern of lower growth velocity across the third trimester, especially those conceived with donated oocytes. The former represents a sub-group at the highest risk of placental dysfunction that may warrant closer follow-up.

Fetal growth disorders following medically assisted reproduction: due to maternal context or techniques? A national French cohort study

RESEARCH QUESTION

What part do maternal context and medically assisted reproduction (MAR) techniques play in the risk of fetal growth disorders?

DESIGN

This retrospective nationwide cohort study uses data available in the French National Health System database and focuses on the period from 2013 to 2017. Fetal growth disorders were divided into four groups according to the origin of pregnancy: fresh embryo transfer (n = 45,201), frozen embryo transfer (FET, n = 18,845), intrauterine insemination (IUI, n = 20,179) and natural conceptions (n = 3,412,868). Fetal growth disorders were defined from the percentiles of the weight distribution according to gestational age and sex: small and large for gestational age (SGA and LGA) if <10th and >90th percentiles, respectively. Analyses were performed using univariate and multivariate logistic models.

RESULTS

Compared with births following natural conception, multivariate analysis showed that the risk of SGA was higher for births following fresh embryo transfer and IUI (adjusted odds ratio [aOR] 1.26 [1.22-1.29] and 1.08 [1.03-1.12], respectively) and significantly lower following FET (aOR 0.79 [0.75-0.83]). The risk of LGA was higher for births following FET (aOR 1.32 [1.27-1.38]), especially in artificial cycles when compared with ovulatory cycles (aOR 1.25 [1.15-1.36]). In the subgroup of births without any obstetrical or neonatal morbidity, the same increased risk of SGA and LGA were observed following fresh embryo transfer or IUI and FET (aOR 1.23 [1.19-1.27] or 1.06 [1.01-1.11] and aOR 1.36 [1.30-1.43], respectively).

CONCLUSIONS

An effect of MAR techniques on the risks for SGA and LGA is suggested independently from maternal context and obstetrical or neonatal morbidities. Pathophysiological mechanisms remain poorly understood and should be further evaluated, as well as the influence of embryonic stage and freezing techniques.

Comparison of perinatal outcomes after frozen or fresh embryo transfer: separate analyses of singleton, twin, and sibling live births from a linked national in vitro fertilization registry

OBJECTIVE

To determine whether perinatal outcomes following frozen vs. fresh embryo transfer (ET) differ within singletons, within sets of twins, and between siblings.

DESIGN

Population-based retrospective cohort study.

SETTING

Academic Medical School PATIENT(S): 200,075 live births in 151,561 women who underwent in vitro fertilization with frozen or fresh ET between 1992 and 2017.

MAIN OUTCOME MEASURE(S)

Gestational age at birth, birthweight, congenital anomaly, and healthy baby (≥37 weeks of gestation, birthweight 2,500-4,000 g, no congenital malformations).

RESULT(S)

There were 200,075 live births in 151,561 women including 132,679 singletons, 33,698 sets of twins, and 5,723 pairs of singleton siblings. In singletons, frozen ET was associated with a lower risk of very preterm birth (adjusted relative risk [aRR], 0.83; 95% confidence interval [CI], 0.73, 0.94), preterm birth (aRR, 0.93; 95% CI, 0.88, 0.97), low birthweight (<2,500 g) (aRR, 0.72; 95% CI, 0.68, 0.77), small for gestational age (aRR, 0.66; 95% CI, 0.62, 0.70) and congenital anomaly (aRR, 0.85; 95% CI, 0.78, 0.94), but higher risk of high birthweight (>4,000 g) (aRR, 1.64; 95% CI, 1.58, 1.72) and large for gestational age (aRR, 1.62; 95% CI, 1.55, 1.70) in comparison with fresh ET. In twins, frozen ET was associated with lower risk of very preterm birth (aRR, 0.84; 95% CI, 0.73, 0.97), and low birthweight (aRR, 0.72; 95% CI, 0.68, 0.77), but with a higher chance of a healthy baby (aRR, 1.11; 95% CI, 1.06, 1.16) compared to fresh ET. Singletons conceived following frozen ET had a lower risk of low birthweight (aRR, 0.56; 95% CI, 0.44, 0.74) and being small for gestational age (aRR, 0.54; 95% CI, 0.42, 0.68) than a singleton sibling born after a fresh ET. Frozen ET also was associated with higher risk of high birthweight (aRR, 1.85; 95% CI, 1.54, 2.24) and being large for gestational age (aRR, 1.81; 95% CI, 1.50, 2.20), and also were less likely to be preterm (aRR, 0.81; 95% CI, 0.67, 0.99).

CONCLUSION(S)

Our key finding is that singletons born following a frozen ET are less likely to be small for gestational age than a singleton sibling born following fresh ET but are more likely to be large for gestational age.

The effect of extended cryo-storage following vitrification on embryo competence: a systematic review and meta-analysis

PURPOSE

Few studies explored whether prolonged cryo-storage after vitrification affects embryo competence and perinatal outcomes. This systematic review and meta-analysis aims at highlighting any putative impact of cryo-storage duration on cryo-survival, miscarriage, live birth and major malformations.

METHODS

A systematic review was performed using MEDLINE (PubMed), ISI Web of Knowledge, Scopus and Embase databases up to June 2021. Data were combined to obtain a pooled OR, and meta-analysis was conducted using a random effects model. Out of 1,389 screened abstracts, 22 papers were assessed for eligibility, and 5 studies were included (N = 18,047 embryos). Prolonged cryo-storage was defined as > 12 months (N = 3389 embryos). Subgroup analysis was performed for untested vitrified cleavage stage embryos (N = 1739 embryos) and for untested and euploid vitrified blastocysts (N = 13,596 and 2712 embryos, respectively).

RESULTS

Survival rate, miscarriage, live birth and major malformation rates were all similar in the two groups.

CONCLUSION

These data further support the safety of long-term cryo-storage of human embryos beyond 12 months. This is reassuring for good prognosis patients with surplus embryos, couples seeking a second child from supernumerary embryos and women postponing the transfer for clinical or personal reasons.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Metabolic Disease Programming: From Mitochondria to Epigenetics, Glucocorticoid Signalling and Beyond

Embryonic and foetal development are critical periods of development in which several environmental cues determine health and disease in adulthood. Maternal conditions and an unfavourable intrauterine environment impact foetal development and may programme the offspring for increased predisposition to metabolic diseases and other chronic pathologic conditions throughout adult life. Previously, non-communicable chronic diseases were only associated with genetics and lifestyle. Now the origins of non-communicable chronic diseases are associated with early-life adaptations that produce long-term dysfunction. Early-life environment sets the long-term health and disease risk and can span through multiple generations. Recent research in developmental programming aims at identifying the molecular mechanisms responsible for developmental programming outcomes that impact cellular physiology and trigger adulthood disease. The identification of new therapeutic targets can improve offspring's health management and prevent or overcome adverse consequences of foetal programming. This review summarizes recent biomedical discoveries in the Developmental Origins of Health and Disease (DOHaD) hypothesis and highlight possible developmental programming mechanisms, including prenatal structural defects, metabolic (mitochondrial dysfunction, oxidative stress, protein modification), epigenetic and glucocorticoid signalling-related mechanisms suggesting molecular clues for the causes and consequences of programming of increased susceptibility of offspring to metabolic disease after birth. Identifying mechanisms involved in DOHaD can contribute to early interventions in pregnancy or early childhood, to re-set the metabolic homeostasis and break the chain of subsequent events that could lead to the development of disease.

Frozen embryo transfer and preeclampsia: where is the link?

PURPOSE OF REVIEW

Preeclampsia is the leading cause of maternal death and has a higher incidence in patients undergoing assisted reproduction treatments. New studies about the mechanisms by which it is more frequent in this population have emerged. The purpose of this review is to gather current information about the available results on this correlation and its possible physiopathology.

RECENT FINDINGS

Recent publications on the physiopathology of preeclampsia indicate that the corpus luteum is the main source of hormonal production until placental formation and that apart from the secretion of estrogen and progesterone, corpus luteum also produces important substances involved in maternal circulatory adaptation, such as relaxin.With the recent increasing number of frozen embryos transfer in natural cycles or under hormonal replacement, this adaptive circulatory process may be unbalanced and predispose this population to preeclampsia.

SUMMARY

This article provides a review of frozen embryo transfer and available protocols, the highest incidence of gestational hypertensive disorders presented by the infertile population and an overview of the possible impact of the absence of corpus luteum on the genesis of this disease.

Associations of IVF singleton birthweight and gestation with clinical treatment and laboratory factors: a multicentre cohort study

STUDY QUESTION

Do IVF treatment and laboratory factors affect singleton birthweight (BW)?

SUMMARY ANSWER

BWs of IVF-conceived singleton babies are increasing with time, but we cannot identify the specific treatment factors responsible.

WHAT IS KNOWN ALREADY

IVF-conceived singleton babies from fresh transfers have slightly lower BW than those conceived naturally, whilst those from frozen embryo transfer (FET) cycles are heavier and comparable to naturally conceived offspring. Our recent studies have shown that BW varies significantly between different IVF centres, and in a single centre, is also increasing with time, without a corresponding change in BWs of naturally conceived infants. Although it is likely that factors in the IVF treatment cycle, such as hormonal stimulation or embryo laboratory culture conditions, are associated with BW differences, our previous study designs were not able to confirm this.

STUDY DESIGN, SIZE, DURATION

Data relating to BW outcomes, IVF treatment and laboratory parameters were collated from pre-existing electronic records in five participating centres for all singleton babies conceived between August 2007 and December 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Seven thousand, five hundred and eighty-eight births, 6207 from fresh and 1381 from FET. Infants with severe congenital abnormalities were excluded. The primary outcome of gestation-adjusted BW and secondary outcomes of unadjusted BW and gestation were analysed using multivariable regression models with robust standard errors to allow for the correlation between infants with the same mother. The models tested treatment factors allowing for confounding by centre, time and patient characteristics. A similar matched analysis of a subgroup of 379 sibling pairs was also performed.

MAIN RESULTS AND THE ROLE OF CHANCE

No significant associations of birth outcomes with IVF embryo culture parameters were seen independent of clinic or time, including embryo culture medium, incubator type or oxygen level, although small differences cannot be ruled out. We did not detect any significant differences associated with hormonal stimulation in fresh cycles or hormonal synchronization in FET cycles. Gestation-adjusted BW increased by 13.4 (95% CI 0.6-26.1) g per year over the period of the study, and babies born following FET were 92 (95% CI 57-128) g heavier on average than those from the fresh transfer.

LIMITATIONS, REASONS FOR CAUTION

Although no specific relationships have been identified independent of clinic and time, the confidence intervals remain large and do not exclude clinically relevant effect sizes. As this is an observational study, residual confounding may still be present.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrates the potential for large scale analysis of routine data to address critical questions concerning the long-term implications of IVF treatment, in accordance with the Developmental Origins of Health and Disease hypothesis. However, much larger studies, at a national scale with sufficiently detailed data, are required to identify the treatment parameters associated with differences in BW or other relevant outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the EU FP7 project grant, EpiHealthNet (FP7-PEOPLE-2012-ITN-317146). No competing interests were identified.

TRIAL REGISTRATION NUMBER

N/A.

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

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

The freeze-all strategy after IVF: which indications?

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

Perinatal and obstetric outcomes in singleton pregnancies following fresh versus cryopreserved blastocyst transfer: a meta-analysis

The transfer of cryopreserved blastocysts is increasing in IVF centres. However, little is known about the perinatal and obstetric outcomes of this procedure. In an attempt to further elucidate these issues, a systematic review and meta-analysis was conducted to compare cryopreserved transfer with fresh blastocyst embryo transfer. The results show that the risk of both preterm (odds ratio [OR] 0.89, 95% confidence interval [CI] 0.80-0.99, P = 0.04) and low birthweight births (OR 0.82, 95% CI 0.68-0.99, P = 0.04) was significantly lower after cryopreserved blastocyst transfer than after fresh blastocyst transfer. The rate of large for gestational age births was significantly higher (OR 1.68, 95% CI 1.55-1.82, P < 0.00001) and the rate of small for gestational age births significantly lower (OR 0.59, 95% CI 0.54-0.65, P < 0.00001) after cryopreserved blastocyst transfer. The transfer of cryopreserved blastocysts was associated with a significantly lower risk of placental abruption (OR 0.58, 95% CI 0.40-0.83, P = 0.003) but a significantly higher risk of Caesarean section (OR 1.21, 95% CI 1.01-1.43, P = 0.03). In conclusion, the perinatal and obstetric outcomes associated with the transfer of cryopreserved blastocysts differ from those associated with fresh blastocyst transfer.

Uterine artery Doppler in singleton pregnancies conceived after in-vitro fertilization or intracytoplasmic sperm injection with fresh vs frozen blastocyst transfer: longitudinal cohort study

OBJECTIVE

Pregnancies conceived by frozen blastocyst transfer (FBT) have higher gestational age and weight at birth as compared to those derived by fresh blastocyst transfer. The aim of this study was to evaluate uterine artery pulsatility index (UtA-PI) in pregnancies conceived by in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) techniques using fresh vs cryopreserved blastocysts.

METHODS

This was a prospective longitudinal study of viable singleton IVF/ICSI pregnancies conceived after FBT or fresh blastocyst transfer, that underwent serial ultrasound assessment at San Raffaele Hospital, Milan, Italy at 7-37 gestational weeks. We excluded pregnancies conceived using other assisted reproductive techniques such as egg donation, twin gestation, pregnancy with abnormality and those resulting in miscarriage. Pregnant women underwent ultrasound assessment at 7-10, 11-14, 18-25 and 26-37 weeks' gestation. Mean UtA-PI was measured using Doppler ultrasound according to The Fetal Medicine Foundation criteria. Pregnancy outcomes were recorded. The primary outcome was mean UtA-PI measurement and secondary outcomes were gestational age at birth, birth weight and fetal and maternal complications, including small-for-gestational age (SGA), pre-eclampsia and large-for-gestational age. UtA-PI values were made Gaussian after log₁₀ transformation. Analysis of repeated measures using a multilevel linear mixed model (fixed effects and random effects) was performed. The possible effect of other covariates on UtA-PI Doppler values, including body mass index, SGA and pre-eclampsia, was also evaluated.

RESULTS

A total of 367 IVF/ICSI cycles, comprising 164 with fresh blastocyst transfer and 203 with FBT, were included and a total of 625 observations (median, 2.5 (range, 1-4)) were collected and analyzed. The FBT group had on average 14% lower UtA-PI compared with the fresh-blastocyst-transfer group. In pregnancies with SGA fetuses, UtA-PI was 18% higher compared to pregnancies without, irrespective of the study group. Pregnancies that underwent fresh blastocyst transfer had significantly lower birth-weight centile (43.4 ± 23.3 vs 50.0 ± 23.1; P = 0.007) and a higher rate of SGA (7.9% vs 2.0%; P = 0.008) compared to those that underwent FBT. No significant differences were found between the two groups with respect to gestational age at birth and rates of preterm birth, pre-eclampsia, gestational diabetes mellitus and large-for-gestational age.

CONCLUSION

UtA-PI and the proportion of SGA are lower in IVF/ICSI pregnancies conceived after FBT as compared to fresh blastocyst transfer. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Should we still perform fresh embryo transfers in ART?

An increasing number of researchers have alluded to the potential benefit of deferring the transfer of embryos produced during assisted reproductive technologies (ARTs) away from ovarian stimulation, using cryopreservation to enable this. The scientific evidence that may justify this recent trend in the use of the so-called 'freeze-all strategy' includes early, mostly small randomised controlled trials that have demonstrated an increase in live birth rates after elective embryo cryopreservation in certain patient populations, as well as evidence from cohort studies and retrospective analyses. What are the risks and benefits of freeze-all strategies in ART, who are the patients in whom it is likely to be advantageous, and does the current evidence allow us to identify situations when deciding that a fresh embryo transfer would be counter-productive? ART professionals are often faced with challenging clinical decisions regarding the best course of treatment for their patient. The purpose of this opinion paper is to provide a clinical guide for whether to perform a fresh embryo transfer or to opt for freezing all embryos in specific situations.

Large-for-gestational age is male-gender dependent in artificial frozen embryo transfers cycles: a cohort study of 1295 singleton live births

RESEARCH QUESTION

What is the effect of frozen embryo transfer (FET) on infant birth weight outcomes and which variables predic large-for-gestational age (LGA) infants.

DESIGN

In a large cohort study, the birth weight of 1295 singleton live births from blastocyst freeze-all-IVF treatments carried out between February 2015 and February 2017 at a single IVF centre were analysed. All embryo transfers were vitrified-warmed blastocyst transfers in artificial FET cycles, with patients having one (n = 864) or two (n = 431) blastocysts transferred. All live births were from ultrasound confirmed single fetal heart pregnancies.

RESULTS

The mean gestational age at delivery was 38.2 (±1.7) weeks, with a 1.11 : 1 female to male ratio for infants delivered. The small and large-for-gestational age rates were 5.02 and 13.28%, with 81.7% of infants appropriate for gestational age. In a multiple logistic regression analysis, the independent variables selected in the model to predict having an LGA infant were maternal parity, infant gender and maternal body mass index (BMI). The risk for LGA at term was significantly higher for male infants when adjusting for maternal parity and BMI (2.8 OR 1.805 to 4.450; P < 0.001).

CONCLUSION

The present study showed that fetal growth of artificial cycle FET pregnancies resulted in an 13.28% LGA infant rate that was mostly male gender dependent.

Clinical outcomes after transfer of blastocysts derived from frozen-thawed cleavage embryos: a retrospective propensity-matched cohort study

PURPOSE

To evaluate the clinical outcomes after fresh transfer of blastocysts cultured from vitrified-thawed cleavage embryos (VTCE) compared with conventional frozen-thawed blastocysts transfer (FBT), or with the usual fresh blastocysts transfer (FRBT).

METHODS

A total of 155 cycles undergoing fresh transfer of VTCE blastocysts, 4904 cycles undergoing FBT, and 1014 cycles undergoing FRBT were retrospectively analyzed from August 2014 to July 2017. Pregnancy, delivery, and neonatal outcomes were compared after propensity score matching.

RESULTS

VTCE blastocysts' transfer resulted in a lower risk of early miscarriage (8.82% versus 19.70%, P < 0.05) and a decreased fetal birth weight (2611.90 ± 618.65 g versus 2931.86 ± 546.52 g, P < 0.01) compared to FBT. No significant difference was found regarding live birth rate, gestational age, and cesarean section. Correspondingly, VTCE blastocysts' transfer led to significantly compromised pregnancy outcomes regarding clinical pregnancy rate and implantation, and even a slightly compromised live birth rate when compared with FRBT. Moreover, a higher occurrence of cesarean Section (88.89% versus 71.29%, P < 0.05) and a shorter gestational age (262.04 ± 14.99 days versus 268.06 ± 14.07, P < 0.05) were also found. Nevertheless, the risk of small for gestational age and large for gestational age, and the neonatal birth weight were comparable.

CONCLUSIONS

VTCE blastocysts' transfer results in a comprehensively moderate outcome, which is an acceptable option for patients. Our results can provide efficient value for patients' counseling. Furthermore, these findings indicate directions for exploring the mechanisms of low birth weight and short gestational age.

Large for gestational age and macrosomia in singletons born after frozen/thawed embryo transfer (FET) in assisted reproductive technology (ART)

Increase in success rates with frozen embryo transfer (FET) and reduced risk of ovarian hyperstimulation syndrome (OHSS) and multiple pregnancies has lead to a steady rise in FET. Further, FET is associated with lower risk of prematurity and low birth weight in singletons, when compared with fresh transfer. However, there is a growing concern of increased risk of large for gestational (LGA) and/or macrosomic children after FET. Macrosomic/LGA births have a higher risk of cesarean section, fetal hypoxia and stillbirth. Improvements in cryopreservation techniques indicate that FET is a trend expected to continue and a freeze-all policy has lately been introduced. With this review, we wished to evaluate the association between FET and LGA and/or macrosomia. We searched electronic databases on January 12, 2018. Ten studies on LGA and six studies on macrosomia were eligible for meta-analysis. We found that the risk of LGA in FET was increased 1.5-fold (AOR = 1.50 95% CI 1.44-1.57 p < 0.001) compared to fresh cycles and 1.3-fold (AOR = 1.31 95% CI 1.20-1.43 p < 0.001) compared to natural conception (NC). Similarly we found a 1.7-fold increased risk of macrosomia in FET compared to fresh transfer (AOR = 1.71 95% CI 1.59-1.83 p < 0.001) and a 1.4-fold increased risk compared to NC (AOR = 1.42 95% CI 1.17-1.71 p < 0.001). Whether the increased risk of LGA and macrosomia is associated with higher long-term health risks remains unknown. Future studies should explore epigenetics modifications in children born after FET and predictors of long-term diseases need to be examined further with longitudinal studies.

[Comparison of birth weights of children born after slow frozen embryo replacement versus fresh embryo transfer]

OBJECTIVE

It is already known that children born after slow frozen embryo replacement have a significantly higher birth weight compared to children born after fresh embryo transfer. Similar data have been reported related to frozen embryo transfer using an open vitrification system. However, few data relative to birth weight using a complete embryo closed vitrification system has been reported. The purpose of this study was to know if frozen embryo in closed vitrification system is associated with a higher birth weight compared to fresh embryo replacement.

DESIGN

This was a monocentric retrospective cohort study, 371 children were issued from fresh embryo replacement and 127 from vitrified embryo transfer.

MATERIALS AND METHODS

All singletons born after fresh or vitrified embryo transfer between January 2011 and April 2015 were included. Births from the vitrified or fresh transfers of egg or sperm donation, and preimplantation genetic diagnosis were excluded. In addition, pregnancies with more than one gestational sac at the first ultrasound were excluded. An analysis of covariance (ANCOVA) was used for multivariate analysis.

RESULTS

Mean birth weight was 205g higher in the frozen embryo compared with fresh embryos transfer groups (3368g vs. 3163g respectively, P<0.001). This difference remained after multivariate analysis adjusted on confounding factors such as gestational age, maternal age, maternal body mass index (BMI), tobacco exposure, number of embryo transferred and birth order (P<0.001)..

CONCLUSIONS

Embryo frozen in closed vitrification system is associated with a higher birth weight compared to fresh embryo replacement. Our findings are consistent with the previous studies related to slow freezing and open vitrification systems data. The effects of controlled ovarian stimulation (COS), ex vivo culture conditions and cryopreservation systems on birth weight of children born should be further explored.

[Birth weight and frozen embryo transfer: State of the art]

The aim of this study was to update our acknowledgment if there is a link between assisted embryo cryopreservation and epigenetics in human? Animal studies have demonstrated epigenetics consequence and especially imprinting disorders due to in vitro culture. In human, it is important to note that after frozen embryo transfer birth weight is significantly increased by 81 to 250g. But these studies cannot identify the reasons of such difference. This review strongly suggests that embryo cryopreservation is responsible for birth weight variations but mechanisms not yet elucidated. Epigenetics is probably one of these but to date, none study is able to prove it. We have to be attentive on a possible link between assisted reproductive technology (ART) and epigenetics reprogrammation.

Perinatal outcomes in children born after fresh or frozen embryo transfer: a Catalan cohort study based on 14,262 newborns

OBJECTIVE

To ascertain whether perinatal outcomes are affected by vitrification and/or controlled ovarian hyperstimulation (COH).

DESIGN

Register-based cohort study.

SETTING

Not applicable.

PATIENT(S)

Women undergoing in vitro fertilization (IVF) between 2008 and 2012 using autologous or donated eggs who had a singleton pregnancy delivered from the 24th week onward.

INTERVENTION(S)

Fresh embryo transfer (ET) or frozen-thawed ET in women undergoing IVF.

MAIN OUTCOME MEASURE(S)

Primary outcome birthweight, and secondary outcomes gestational age at delivery, small for gestational age, mode of delivery, and perinatal mortality.

RESULT(S)

In the autologous egg population, newborns from the fresh ET group had lower birthweight than the frozen-thawed ET group (3,152.9 ± 545.5g and 3,343.2 ± 532.3g, respectively), and this difference persisted even after adjusting for confounding factors, and the newborns had a higher risk of being small for gestational age (SGA). In contrast, among egg-donor recipients undergoing ET, the mean birthweight did not differ between the groups (3,165 ± 604.15 g and 3,143.60 ± 604.21g in the fresh and frozen-thawed ET groups, respectively); however, in the adjusted regression model birthweight was statistically significantly higher in the fresh ET group than the frozen-thawed ET group. The risk of SGA remained comparable between the fresh versus frozen-thawed ET groups. We observed no statistically significant differences in perinatal mortality between groups either in the autologous egg population or in the donor recipient group.

CONCLUSION(S)

Perinatal outcomes are negatively affected by COH and not affected by the vitrification process.

Increased risk of large-for-gestational age birthweight in singleton siblings conceived with in vitro fertilization in frozen versus fresh cycles

BACKGROUND

Children born from fresh in vitro fertilization (IVF) cycles are at greater risk of being born smaller and earlier, even when limited to singletons; those born from frozen cycles have an increased risk of large-for-gestational age (LGA) birthweight (z-score ≥1.28). This analysis sought to overcome limitations in other studies by using pairs of siblings, and accounting for prior cycle outcomes, maternal characteristics, and embryo state and stage.

METHODS

Pairs of singleton births conceived with IVF and born between 2004 and 2013 were identified from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System database, matched for embryo stage (blastocyst versus non-blastocyst) and infant gender, categorized by embryo state (fresh versus frozen) in 1st and 2nd births (four groups).

RESULTS

The data included 7795 singleton pairs. Birthweight z-scores were 0.00-0.04 and 0.24-0.26 in 1st and 2nd births in fresh cycles, and 0.25-0.34 and 0.50-0.55 in frozen cycles, respectively. LGA was 9.2-9.8 and 14.2-15.4% in 1st and 2nd births in fresh cycles, and 13.1-15.8 and 20.8-21.0% in 1st and 2nd births in frozen cycles. The risk of LGA was increased in frozen cycles (1st births, adjusted odds ratios (AOR) 1.74, 95% CI 1.45, 2.08; and in 2nd births when the 1st birth was not LGA, AOR 1.70, 95% CI 1.46, 1.98 for fresh/frozen and 1.40, 1.11, 1.78 for frozen/frozen).

CONCLUSIONS

Our results with siblings indicate that frozen embryo state is associated with an increased risk for LGA. The implications of these findings for childhood health and risk of obesity are unclear, and warrant further investigation.

Neonatal outcomes in pregnancies resulting from oocyte donation: a cohort study in Sweden

Background

Pregnancies resulting through oocyte donation have been associated with increased risk for adverse outcomes for the mother, such as gestational hypertensive disorders. However, little is known about possible neonatal complications of such pregnancies. The purpose of this study was to evaluate the neonatal health outcomes among singleton pregnancies in a population of relatively young and healthy oocyte recipients in Sweden, taking into account the medical indication leading to treatment.

Methods

This cohort study involved 76 women conceiving with donated oocytes, 149 age-matched nulliparous women conceiving spontaneously and 63 women conceiving after non-donor IVF. Participants were recruited during 2005–2008 and followed up until delivery. Data on neonatal outcomes were retrieved from the National Birth Medical Register and the medical records of oocyte recipients from seven Swedish University Hospitals with IVF clinics. Logistic regression analyses were performed to examine the association of mode of conception and neonatal outcomes, adjusted for maternal age and BMI, gestational age and delivery by cesarean section.

Results

Infants conceived through oocyte donation had higher odds for premature delivery [OR 2.36, 95 % CI (1.02–5.45)], for being small for gestational age [OR 4.23, 95 % CI (1.03–17.42)] and having Apgar score below 7 at 5 min [OR 10.57, 95 % CI (1.21–92.20)] compared to spontaneously conceived infants. Similar trends were observed when comparing infants conceived through oocyte donation to those conceived by traditional IVF. Furthermore, donor oocyte infants had a lower mean birthweight and length compared to autologous oocyte neonates (p = 0.013); however no differences were noted among infants born at term. Neonatal outcomes were more favorable among women with diminished ovarian reserve compared to those with other indications for oocyte donation.

Conclusions

Infants conceived after oocyte donation in Sweden have higher odds of being born prematurely and having lower mean birthweight in comparison to non-donor infants.

It seems that these unfavorable neonatal outcomes are present despite the age, weight and health restrictions applied to recipients before oocyte donation treatment in Sweden.

Segmented ART - The new era in ART?

Currently up to 4% of infants born in developing countries are conceived through assisted reproductive technology (ART). Even though most of these conceptions occur and progress without complications, ART procedures and processes may increase iatrogenesis through complications in - and after conception. We herein review and discuss the clinically and scientific implications and evidence of iatrogenesis, and show how the evolution in ART technologies and procedures has led to the current presumption that frozen embryo transfer might be a more optimal strategy than fresh embryo transfer, in terms of not only reproduction, but also of maternal and fetal outcomes. There is increasing scientific evidence to support the notion that controlled ovarian stimulation could induce significant changes to the endocrine profile of a reproductive cycle, especially to the reproductively important early luteal phase. These changes may not only have a negative effect on implantation and early placentation, but also on the mother, the fetus, and the infant. The overt consequences of controlled ovarian stimulation include ovarian hyperstimulation syndrome, reduced embryo implantation, increased ectopic pregnancy, and altered placentation and fetal growth. The cumulative scientific evidence from this review suggests that GnRHa trigger in segmented ART might constitute the future routine treatment regimen for IVF patients, providing a safe, effective, and patient friendly treatment.