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

Differences in perinatal complications and serum hormone levels due to uterine endometrial preparation methods in frozen-thawed embryo transfer

AIM

In frozen-thawed embryo transfer (FET), differences in endometrial preparation methods affect the incidence of perinatal complications. However, the underlying causes are unclear. We aimed to investigate whether serum E2, P4 levels are associated with perinatal complications.

METHODS

This is a retrospective cohort study, involving 306 successful FET pregnancies from 2017 to 2022. Participants were divided into Natural Cycle (NC) and Hormone Replacement Cycle (HRC) group. We compared serum hormone levels, maternal backgrounds, and perinatal outcomes and complications. Furthermore, within the HRC group, serum hormone levels were compared for perinatal complications previously reported to show differences in incidence rates depending on the method of endometrial preparation.

RESULTS

HRC exhibited significantly higher serum E2 levels during the implantation period, but lower P4 levels during ovulation, implantation, and pregnancy test period compared with NC. HRC also had significantly higher rates of postpartum hemorrhage (PPH) and placenta accreta spectrum (PAS). There was no association found between perinatal complications more likely to occur in HRC and serum E2, P4 levels.

CONCLUSIONS

In HRC, there were more occurrences of PPH and PAS. Although serum E2, P4 levels during FET did not correlate with perinatal complications.

Effect of ART treatments on maternal and neonatal outcomes in singleton live births: A large-scale retrospective cohort study

Background

The increased risk of pregnancy complications in the ART population has been reported, but the source of these risks remains controversial. The study aims to evaluate the association between ART treatments and patient characteristics with maternal and neonatal outcomes.

Methods

This was a retrospective analysis of 45,159 singleton pregnant women at a hospital between 2018 and 2021. The maternal and neonatal outcomes included pregnancy-induced hypertension (PIH), preeclampsia (PE), gestational diabetes mellitus (GDM), placental abruption (PA), placenta accreta spectrum (PAS), postpartum hemorrhage (PPH), cesarean section, iatrogenic and spontaneous preterm birth, small for gestational age (SGA), low birth weight (LBW), macrosomia, and birth defects. We assessed the outcomes among the fresh embryo transfer (ET), frozen embryo transfer (FET), and spontaneous conception (SC) groups. Potential risk factors were further analyzed in the ART population.

Results

FET was associated with higher risks for PIH (SC: AOR, 1.97(1.51-2.57); fresh ET: AOR, 1.68(1.03-2.72)), PE (SC: 2.28(1.86-2.80); fresh ET: AOR, 1.61(1.11-2.33)), PAS (SC: AOR, 3.89(3.39-4.46); fresh ET: AOR, 2.23(1.70-2.92)), PPH (SC: AOR, 3.46(2.76-4.34)); fresh ET: 2.09(1.39-3.14)), and macrosomia (SC: 1.53(1.25-1.86); fresh ET: AOR, 2.87(1.89-4.35). Fresh ET was associated with higher risks for PA (SC: AOR, 2.19(1.51-3.18); FET: AOR, 0.39(0.17-0.90)), SGA (SC: AOR, 1.56(1.06-2.31), FET: AOR, 0.42(0.19-0.91)), and LBW (SC: AOR, 2.24(1.82-2.77), FET: AOR, 0.63 (0.44-0.89)), and fresh ET is an independent risk factor for PA and SGA. Furthermore, the risk of GDM was associated with the biological characteristic of low-fertility patients.

Conclusions

Embryo status (fresh or frozen) is a key factor affecting the maternal and neonatal outcomes in ART treatments, while biological characteristics of infertile patients also play a certain role.

Is large for gestational age in singletons born after frozen embryo transfer associated with freezing technique or endometrial preparation protocol? A longitudinal national French study

STUDY QUESTION

Is large for gestational age (LGA) observed in babies born after frozen embryo transfer (FET) associated with either the freezing technique or the endometrial preparation protocol?

SUMMARY ANSWER

Artificial cycles are associated with a higher risk of LGA, with no difference in rate between the two freezing techniques (vitrification versus slow freezing) or embryo stage (cleaved embryo versus blastocyst).

WHAT IS KNOWN ALREADY

Several studies have compared neonatal outcomes after fresh embryo transfer (ET) and FET and shown that FET is associated with improved neonatal outcomes, including reduced risks of preterm birth, low birthweight, and small for gestational age (SGA), when compared with fresh ET. However, these studies also revealed an increased risk of LGA after FET. The underlying pathophysiology of this increased risk remains unclear; parental infertility, laboratory procedures (including embryo culture conditions and freezing-thawing processes), and endometrial preparation treatments might be involved.

STUDY DESIGN, SIZE, DURATION

A multicentre epidemiological data study was performed through a retrospective analysis of the standardized individual clinical records of the French national register of IVF from 2014 to 2018, including single deliveries resulting from fresh ET or FET that were prospectively collected in fertility centres. Complementary data were collected from the participating fertility centres and included the vitrification media and devices, and the endometrial preparation protocols.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were collected from 35 French ART centres, leading to the inclusion of a total of 72 789 fresh ET, 10 602 slow-freezing FET, and 39 062 vitrification FET. Main clinical outcomes were presented according to origin of the transferred embryos (fresh, slow frozen, or vitrified embryos) and endometrial preparations for FET (ovulatory or artificial cycles), comparing five different groups (fresh, slow freezing-ovulatory cycle, slow freezing-artificial cycle, vitrification-ovulatory cycle, and vitrification-artificial cycle). Foetal growth disorders were defined in live-born singletons according to gestational age and sex-specific weight percentile distribution: SGA and LGA if <10th and ≥90th percentiles, respectively. Analyses were performed using linear mixed models with the ART centres as random effect.

MAIN RESULTS AND THE ROLE OF CHANCE

Transfers led to, respectively, 19 006, 1798, and 9195 deliveries corresponding to delivery rates per transfer of 26.1%, 17.0%, and 23.5% after fresh ET, slow-freezing FET, and vitrification FET, respectively. FET cycles were performed in either ovulatory cycles (n = 21 704) or artificial cycles (n = 34 237), leading to 5910 and 10 322 pregnancies, respectively, and corresponding to pregnancy rates per transfer of 31.6% and 33.3%. A significantly higher rate of spontaneous miscarriage was observed in artificial cycles when compared with ovulatory cycles (33.3% versus 21.4%, P < 0.001, in slow freezing groups and 31.6% versus 21.8%, P < 0.001 in vitrification groups). Consequently, a lower delivery rate per transfer was observed in artificial cycles compared with ovulatory cycles both in slow freezing and vitrification groups (15.5% versus 18.9%, P < 0.001 and 22.8% versus 24.9%, P < 0.001, respectively). Among a total of 26 585 live-born singletons, 16 413 babies were born from fresh ET, 1644 from slow-freezing FET, and 8528 from vitrification FET. Birthweight was significantly higher in the FET groups than in the fresh ET group, with no difference between the two freezing techniques. Likewise, LGA rates were higher and SGA rates were lower in the FET groups compared with the fresh ET group whatever the method used for embryo freezing. In a multivariable analysis, the risk of LGA following FET was significantly increased in artificial compared with ovulatory cycles. In contrast, the risk of LGA was not associated with either the freezing procedure (vitrification versus slow freezing) or the embryo stage (cleaved embryo versus blastocyst) at freezing. Regarding the vitrification method, the risk of LGA was not associated with either the vitrification medium used or the embryo stage.

LIMITATIONS, REASONS FOR CAUTION

No data were available on maternal context, such as parity, BMI, infertility cause, or maternal comorbidities, in the French national database. In particular, we cannot exclude that the increased risk of LGA observed following FET with artificial cycles may, at least partially, be associated with a confounding effect of some maternal factors. No information about embryo culture and incubation conditions was available. Most of the vitrification techniques were performed using the same device and with two main vitrification media, limiting the validity of a comparison of risk for LGA according to the device or vitrification media used.

WIDER IMPLICATIONS OF THE FINDINGS

Our results seem reassuring, since no potential foetal growth disorders following embryo vitrification in comparison with slow freezing were observed. Even if other factors are involved, the endometrial preparation treatment seems to have the greatest impact on LGA risk following FET. FET during ovulatory cycles could minimize the risk for foetal growth disorders.

STUDY FUNDING/COMPETING INTEREST(S)

This work has received funding from the French Biomedicine Agency (Grant number: 19AMP002). None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Do IVF culture conditions have an impact on neonatal outcomes? A systematic review and meta-analysis

PURPOSE

Are embryo culture conditions, including type of incubator, oxygen tension, and culture media, associated with obstetric or neonatal complications following in vitro fertilization (IVF)?

METHODS

A systematic search of MEDLINE, EMBASE, and Cochrane Library was performed from January 01, 2008, until October 31, 2021. The studies reporting quantitative data on at least one of the primary outcomes (birthweight and preterm birth) for the exposure group and the control group were included. For oxygen tension, independent meta-analysis was performed using Review Manager, comparing hypoxia/normoxia. For culture media, a network meta-analysis was carried out using R software, allowing the inclusion of articles comparing two or more culture media.

RESULTS

After reviewing 182 records, 39 full-text articles were assessed for eligibility. A total of 28 studies were kept for review. Meta-analysis about the impact of incubator type on perinatal outcomes could not be carried out because of a limited number of studies. For oxygen tension, three studies were included. The pairwise meta-analysis comparing hypoxia/normoxia did not show any statistical difference for birthweight and gestational age at birth. For culture media, 18 studies were included. The network meta-analysis failed to reveal any significant impact of different culture media on birthweight or preterm birth.

CONCLUSION

No difference was observed for neonatal outcomes according to the embryo culture conditions evaluated in this review. Further research is needed about the safety of IVF culture conditions as far as future children's health is concerned.

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.

Impacts of different culture times on pregnancy outcomes after thawing of cleavage stage embryos

OBJECTIVE

This study assessed the impacts of in vitro culture times of cleavage embryos on clinical pregnancy outcomes.

METHODS

This retrospective cohort study was performed at the Reproductive Medicine Department of Hainan Modern Women and Children's Hospital in China between January 2018 and December 2022. Patients who first underwent frozen embryo transfer with in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles on day 3 were included. According to the time of embryo culture after thawing, the embryos were divided into long-term culture group(18-20 h) and short-term culture group (2-4 h). The clinical pregnancy rate was regarded as he primary outcome. To minimize confounding factors and reduce selection bias, the propensity score matching was used to balance the effects of known confounding factors and to reduce selection bias. Stratified analyses and multiple logistic regression analyses were used to evaluate the risk factors affecting the clinical pregnancy outcomes after matching.

RESULTS

General characteristics between two groups were comparable after matching. In the long-term culture group, 266/381 (69.81%) embryos had more than 10 blastomeres, and 75/381 (19.68%) reached the morula stage. After overnight culture, the implantation rate (27.97% vs. 14.28%, P = 0.018) and clinical pregnancy rate (38.46% vs. 22.5%, P = 0.05) were increased in the group with proliferating blastomeres. The long-term culture group trended to have a higher clinical pregnancy rate compared with the short-term culture group (35.74% vs. 29.79%). No statistical differences in clinical pregnancy outcomes between the two groups were observed after matching, including the rates of implantation (25.46% vs23.98%), miscarriages (25% vs. 22.85%), ongoing pregnancy rate (76.2% vs. 77.15%) and live birth rate (26.8% vs. 22.98%). Stratified analyses were performed according to the age of the patients. After matching, there were no significant differences in the clinical pregnancy, implantation and miscarriage rates between the two groups for patients > 35 or ≤ 35 years of age. Subgroup analyses were performed according to the quality of the transferred embryos. There were no significant differences in the clinical outcomes, between two groups after embryos transferred with the same quality. Multivariate Logistic regression analysis was used to evaluate the influencing factors of clinical pregnancy outcomes after matching. Culture time was not found to be an independent predictor for clinical pregnancy [OR 0.742, 95%CI 0.487 ~ 1.13; P = 0.165]. The age of oocyte retrieval [OR 0.906, 95%CI 0.865 ~ 0.949; P <0.001] and the number of high-quality embryos transferred [OR 1.787, 95%CI 1.256 ~ 2.543; P = 0.001] were independent factors affecting clinical pregnancy outcomes.

CONCLUSIONS

In vitro 18-20 h culture of embryos with either good-or non-good-quality will not adversely affect the clinical pregnancy.

Semen processing using magnetic-activated cell sorting before ICSI is deemed safe for obstetric and perinatal outcomes: a retrospective multicentre study

RESEARCH QUESTION

Is magnetic-activated cell sorting (MACS) a safe semen sample processing technique for newborns and mothers when used for semen processing prior to intracytoplasmic sperm injection (ICSI) cycles?

DESIGN

This retrospective multicentre cohort study involved patients undergoing ICSI cycles with either donor or autologous oocytes from January 2008 to February 2020. They were divided into two groups: those who underwent standard semen preparation (reference group) and those who had an added MACS procedure (MACS group). A total of 25,356 deliveries were assessed in the case of cycles using donor oocytes, and 19,703 deliveries from cycles using autologous oocytes. Of these, 20,439 and 15,917, respectively, were singleton deliveries. Obstetric and perinatal outcomes were retrospectively assessed. All means, rates and incidences were computed per live newborn in each study group.

RESULTS

There were no significant differences between the main obstetric and perinatal morbidities affecting the mothers' and newborns' well-being between groups using either donated or autologous oocytes. There was a significant increase in the incidence of gestational anaemia in both subpopulations (donor oocytes P = 0.01; autologous oocytes P < 0.001). However, this incidence was within the estimated prevalence for gestational anaemia in the general population. There was a statistically significant decrease in preterm (P = 0.02) and very preterm (P = 0.01) birth rates in the MACS group in cycles using donor oocytes.

CONCLUSIONS

The use of MACS during semen preparation before ICSI using either donor or autologous oocytes appears to be safe for the mothers' and newborns' well-being during pregnancy and birth. Nevertheless, a close follow-up of these parameters in the future is advised, especially concerning anaemia, in order to detect even smaller effect sizes.

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.

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.

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.

High birth weight and greater gestational age at birth in singletons born after frozen compared to fresh embryo transfer

OBJECTIVE

While many studies agree that the fetal birth weight is higher after frozen embryo transfer (FET), few studies have explored the difference in fetal weight change during such pregnancies. This cohort study was to identify the difference in fetal birth weight and gestational age at birth between singletons born following fresh ET and those born following FET.

MATERIALS AND METHODS

This was a hospital-based cohort study using clinical data from the Kaohsiung Chang Gung Memorial Hospital Obstetric and Neonatal Database from January 1, 2007, to December 1, 2018. A sample of 784 eligible women who had singleton pregnancies and live-born deliveries after 428 fresh ET or 356 FET between January 2007 and December 2018.

RESULTS

Compared with those in the fresh ET group, singletons in the FET group had higher birth weight (3137 g [2880-3441 g] vs. 3060 g [2710-3340 g], p < 0.05), were born later (39.0 weeks of gestation [38.0-40.0 weeks] vs. 38.0 weeks of gestation [37.0-39.0 weeks], p < 0.05), and had a lower incidence of preterm birth (10.4% vs. 15.2%, p < 0.05). The difference in birth weight was not associated with maternal body weight (BW) or body mass index, increase in maternal BW in the third trimester, but related to the total increase in maternal BW during pregnancy.

CONCLUSIONS

The birthweight of singletons born following FET and fresh ET became significant in the late third trimester. The main reason is that singletons conceived from FET were at a lower relative risk of preterm delivery and had a higher gestational age at birth.

Associations of maternal obesity, frozen embryos, and offspring adverse cardiometabolic alterations

OBJECTIVE

To evaluate the long-term cardiometabolic health of offspring conceived by frozen embryo transfer and born to mothers with overweight/obesity.

DESIGN

Retrospective cohort study.

SETTING

Center for Reproductive Medicine.

PATIENT(S)

A total of 2,741 offspring born to mothers who underwent in vitro fertilization/intracytoplasmic sperm injection treatment were followed between June 2014 and August 2021. The offspring were singletons aged 4-11 years at follow-up.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Age-specific z-scores of cardiometabolic parameters were examined, including adiposity, systolic/diastolic blood pressure, glucose, and lipid profiles, and the metabolic sum score of different cardiometabolic characteristics.

RESULTS

Of 2,741 offsprings, 965 (35.21%) were born to mothers with overweight/obesity, including 396 (41.04%) offspring who were conceived by frozen embryo transfer. After adjusting for paternal and maternal age, paternal body mass index (BMI), offspring age, offspring sex, and offspring postnatal energy intake, offspring born to mothers with overweight/obesity and conceived by frozen embryo transfer showed a significantly higher BMI z-score, systolic blood pressure z-score, metabolic sum score-1, and metabolic sum score-2 compared with those conceived by fresh embryo transfer (BMI z-score: adjusted mean difference, 0.17; 95% confidence interval [CI], 0.04-0.30; systolic blood pressure z-score: adjusted mean difference, 0.16; 95% CI, 0.02-0.29; metabolic sum score-1: adjusted mean difference, 0.54; 95% CI, 0.15-0.94; metabolic sum score-2: adjusted mean difference, 0.45; 95% CI, 0.07-0.83). However, in offspring of mothers with normal weight, offspring conceived by frozen embryo transfer showed a significantly lower low-density lipoprotein-cholesterol z-score compared with those conceived by fresh embryo transfer (adjusted mean difference, -0.12; 95% CI, -0.22 to -0.02). Other cardiometabolic parameters were comparable between offspring with frozen and fresh embryo transfers after adjusting for multivariate confounder variables.

CONCLUSIONS

This study found that among offspring from mothers who were overweight/obese, those offspring conceived by frozen embryo transfer were associated with higher systolic blood pressure z-scores and adverse metabolic changes compared with those conceived by fresh embryo transfer. The changes show that the association between frozen embryo transfer and offspring adverse cardiometabolic changes is apparent only among those born to mothers who are overweight/obese.

Bibliometric analysis and visualization of literature on assisted reproduction technology

Introduction

Assisted reproductive technology (ART) is a method that uses various techniques to process sperm or ova. Assisted reproductive technology involves removing ova from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman.

Methods

Based on the web of science core collection database, we firstly analyzed the quantity and quality of publications in the field of ART, secondly profiled the publishing groups in terms of country, institution, author's publication and cooperation network, and finally sorted out and summarized the hot topics of research.

Results

In total, 6,288 articles on ART were published between 2001 and 2022 in 1,013 journals. Most of these published articles represent the global research status, potential hotspots and future research directions. Publications and citations of research on assisted reproductive technology have steadily increased over the past few decades. Academic institutions in Europe and the United States have been leading in assisted reproductive technology research. The countries, institutions, journals, and authors with the most published articles were the United States (1864), Harvard Univ (108), Fertility and Sterility (819), and Stern, Judy E. (64). The most commonly used keywords are Assisted reproductive technology (3303) and in-vitro Fertilization (2139), Ivf (1140), Pregnancy (1140), Women (769), Intracytoplasmic Sperm injection (644), In Fertilization (632), Risk (545), and Outcome (423).

Conclusion

Frozen embryo transfer, intracytoplasmic sperm injection, and in vitro fertilization are the main research topics and hotspots in the field of assisted reproductive technology.

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

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

Prenatal growth trajectories and birth outcomes after frozen-thawed extended culture embryo transfer and fresh embryo transfer: the Rotterdam Periconception Cohort

RESEARCH QUESTION

Are there differences in prenatal growth trajectories and birth outcomes between singleton pregnancies conceived after IVF treatment with frozen-thawed extended culture embryo transfer at day 5, fresh embryo transfer at day 3 or naturally conceived pregnancies?

DESIGN

From a prospective hospital-based cohort, 859 singleton pregnancies were selected, including 133 conceived after IVF with frozen-thawed embryo transfer, 276 after fresh embryo transfer, and 450 naturally conceived pregnancies. Longitudinal 3D ultrasound scans were performed at 7, 9 and 11 weeks of gestation for offline crown-rump length (CRL) and embryonic volume measurements. Second trimester estimated fetal weight was based on growth parameters obtained during the routine fetal anomaly scan at 20 weeks of gestation. Birth outcome data were collected from medical records.

RESULTS

No differences regarding embryonic growth trajectories were observed between frozen-thawed and fresh embryo transfer. Birthweight percentiles after fresh embryo transfer were lower than after frozen-thawed embryo transfer (38.0 versus 48.0; P = 0.046, respectively). The prevalence of non-iatrogenic preterm birth (PTB) was significantly lower in pregnancies resulting from fresh embryo transfer compared with frozen-thawed embryo transfer (4.7% versus 10.9%; P = 0.026, respectively). Compared with naturally conceived pregnancies, birthweight percentiles and percentage of non-iatrogenic PTB were significantly lower in pregnancies after fresh embryo transfer and gestational age at birth was significantly higher.

CONCLUSIONS

This study shows that embryonic growth is comparable between singleton pregnancies conceived after fresh and frozen-thawed embryo transfer. The lower relative birthweight and PTB rate in pregnancies after fresh embryo transfer than after frozen-thawed embryo transfer and naturally conceived pregnancies warrants further investigation.

Lower risk of adverse perinatal outcomes in natural versus artificial frozen-thawed embryo transfer cycles: a systematic review and meta-analysis

This systematic review of literature and meta-analysis of observational studies reports on perinatal outcomes after frozen embryo transfer (FET). The aim was to determine whether natural cycle frozen embryo transfer (NC-FET) in singleton pregnancies conceived after IVF decreased the risk of adverse perinatal outcomes compared with artificial cycle frozen embryo transfer (AC-FET). Thirteen cohort studies, including 93,201 cycles, met the inclusion criteria. NC-FET was associated with a lower risk of hypertensive disorders in pregnancy (HDP) (RR 0.61, 95% CI 0.50 to 0.73), preeclampsia (RR 0.47, 95% CI 0.42 to 0.53), large for gestational age (LGA) (RR 0.93, 95% CI 0.90 to 0.96) and macrosomia (RR 0.82, 95% CI 0.69 to 0.97) compared with AC-FET. No significant difference was found in the risk of gestational hypertension and small for gestational age. Secondary outcomes assessed were the risk of preterm birth (RR 0.83, 95% CI 0.79 to 0.88); post-term birth (RR 0.48, 95% CI 0.29 to 0.80); low birth weight (RR 0.84, 95% CI 0.80 to 0.89); caesarean section (RR 0.84, 95% CI 0.77 to 0.91); postpartum haemorrhage (RR 0.39, 95% CI 0.35 to 0.45); placental abruption (RR 0.61, 95% CI 0.38 to 0.98); and placenta accreta (RR 0.18, 95% CI 0.10 to 0.33). All were significantly lower with NC-FET compared with AC-FET. In assessing safety, NC-FET significantly decreased the risk of HDP, preeclampsia, LGA, macrosomia, preterm birth, post-term birth, low birth weight, caesarean section, postpartum haemorrhage, placental abruption and placenta accreta. Further randomized controlled trials addressing the effect of NC-FET and AC-FET on maternal and perinatal outcomes are warranted. Clinicians should carefully monitor pregnancies achieved by FET in artificial cycles prenatally, during labour and postnatally.

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.

Six-year follow-up of children born from vitrified oocytes

RESEARCH QUESTION

Are children born from vitrified-warmed oocytes physically or mentally different from naturally conceived children?

DESIGN

Intracytoplasmic sperm injection (ICSI) of vitrified-warmed oocytes was performed for 282 patients (307 cycles) from August 2000 to March 2020. Long-term follow-up of children born from vitrified-warmed oocytes was performed via a questionnaire that was sent to the parents at regular intervals from 3 to 72 months after the child's birth. Questionnaires were sent 11 times from birth to the age of 6 years. The development of motor function and mental status was evaluated as the primary outcome, based on the reported data. Subsequently, patients were divided into four groups by age at oocyte retrieval (20-29, 30-34, 35-39, and 40 years or older). Clinical outcomes were calculated as a secondary outcome.

RESULTS

For the 282 patients, the birth of 116 babies was reported (110 singletons and three sets of twins), and seven cases are, at the time of writing, unconfirmed. The results of the survey found physical parameters in singletons to be equivalent to the nationally reported average data issued by the Ministry of Health, Labor and Welfare of Japan.

CONCLUSION

This is the first follow-up report of children born from vitrified-warmed oocytes followed by ICSI. The data suggested that the responses from the study participants on the mental and physical development of children were comparable to the data reported by the government, although more responses from patients should be collected to allow further study.

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.

Risk of small for gestational age is reduced after frozen compared with fresh embryo transfer in endometriosis

RESEARCH QUESTION

What are the perinatal outcomes and especially the risk of small for gestational age (SGA) babies born after frozen versus fresh embryo transfer in mothers affected by endometriosis undergoing treatment with assisted reproductive technology (ART)?

DESIGN

A cohort study conducted between November 2012 and October 2017, in which infertile women with endometriosis undergoing ART and achieving singleton pregnancies that lasted beyond 12 weeks of gestation were included. Pregnancies obtained after a frozen embryo transfer (FET) were compared with those obtained after a fresh embryo transfer. A total of 339 pregnant women were included: 112 patients in the fresh embryo transfer group and 227 in the FET group. The main outcome was the rate of SGA. Secondary analyses were performed for adverse pregnancy outcomes and perinatal complications.

RESULTS

Of the included women, 109/112 (97.3%) and 222/227 (97.8%) delivered a live child after at least 24 weeks of gestation in the fresh and in the frozen embryo transfer groups, respectively (P = 0.53). The risk of SGA decreased after a FET compared with a fresh embryo transfer (odds ratio [OR] 0.49 [0.25-0.98], P = 0.04) after multivariable analysis. The mean birthweight and the gestational age at delivery were not significantly different between the two study groups. Other pregnancy and perinatal complications were not statistically different between the two study populations.

CONCLUSIONS

The present study of endometriosis-affected women found a significantly lower risk of SGA in patients undergoing frozen, mainly blastocyst, embryo transfer compared with patients undergoing fresh, mainly cleavage stage, embryo transfer.

Pregnancy Outcomes Following Letrozole Use in Frozen-thawed Embryo Transfer Cycles: A Systematic Review and Meta-analysis

While widely used for ovulation induction in assisted reproductive technology, the clinical efficacy of letrozole for endometrial preparation prior to frozen-thawed embryo transfer (FET) cycles remains yet to be elucidated. We performed a meta-analysis to compare pregnancy outcomes after letrozole use with those of other endometrial preparation protocols in patients undergoing FET. PubMed, Scopus, Embase and the Cochrane Library were searched for eligible studies. Clinical pregnancy rate (CPR), live birth rate (LBR) and birth defect rate (BDR) were analysed using odds ratio (OR) and 95% confidence interval (CI). A total of 10 studies representing 75 968 FET cycles were included. Comparable CPR and LBR were observed when comparing letrozole administration with natural cycle (OR 1.24, 95% CI: 0.69 – 2.24; OR 1.18, 95% CI: 0.60 – 2.32), artificial cycle (OR 1.46, 95% CI: 0.87 – 2.44; OR 1.39, 95% CI: 0.77 – 2.52), and artificial cycle with gonadotropin-releasing hormone agonist suppression (OR 1.11, 95% CI: 0.78 – 1.59; OR 1.18, 95% CI: 0.82 – 1.68). Pooled results of the limited studies comparing letrozole with human menopausal gonadotropin demonstrated a similar CPR between groups (OR 1.46, 95% CI: 0.29 – 7.21, two studies), but the letrozole group had a statistically lower LBR (OR 0.67, 95% CI: 0.52 – 0.86, one study). No increased BDR was observed in the letrozole group compared to natural cycles or artificial cycles (OR 0.98, 95% CI: 0.60 – 1.61; OR 1.39, 95% CI; 0.84 – 2.28). This pooled analysis supports the use of letrozole as an efficacious and safe alternative to mainstream regimens for endometrial preparation in FET cycles.

Timing of exposure to gonadotropins has differential effects on the conceptus: evidence from a mouse model†

Superovulation with gonadotropins alters the hormonal milieu during early embryo development and placentation, and may be responsible for fetal and placental changes observed after in vitro fertilization (IVF). We hypothesized that superovulation has differential effects depending on timing of exposure. To test our hypothesis, we isolated the effect of superovulation on pre- and peri-implantation mouse embryos. Blastocysts were obtained from either natural mating or following superovulation and mating, and were transferred into naturally mated or superovulated pseudopregnant recipient mice. Fetal weight was significantly lower after peri-implantation exposure to superovulation, regardless of preimplantation exposure (p = 0.006). Placentas derived from blastocysts exposed to superovulation pre- and peri-implantation were larger than placentas derived from natural blastocysts that are transferred into a natural or superovulated environment (p < 0.05). Fetal-to-placental weight ratio decreased following superovulation during the pre- or peri-implantation period (p = 0.05, 0.01, respectively) and these effects were additive. Peg3 DNA methylation levels were decreased in placentas derived from exposure to superovulation both pre- and peri-implantation compared with unexposed embryos and exposure of the preimplantation embryo only. Through RNA sequencing on placental tissue, changes were identified in genes involved in immune system regulation, specifically interferon signaling, which has been previously implicated in implantation and maintenance of early pregnancy in mice. Overall, we found that the timing of exposure to gonadotropin stimulation can have differential effects on fetal and placental growth. These findings could impact clinical practice and underscores the importance of dissecting the role of procedures utilized during IVF on pregnancy complications.

Examination of fetal growth trajectories following infertility treatment

PURPOSE

The objective of this retrospective cohort study was to compare fetal growth during the second and third trimesters for ovulation induction with intrauterine insemination (IUI), fresh embryo transfer (ET), frozen embryo transfer (FET), and spontaneous conception following infertility.

METHODS

Three hundred ninety-five women with viable pregnancies confirmed at a single academic fertility center participated. All women achieved pregnancy either by treatment or spontaneously after a diagnosis of infertility. Inclusion criteria included autologous singleton pregnancies. Exclusion criteria included pregnancies from donor oocytes, twins, unavailable ultrasound data, and treatment methods with small number of participants. Primary outcomes of interest were head circumference (HC), abdominal circumference (AC), HC/AC ratio, and estimated fetal weight (EFW). Conditional growth curve models were created, and growth curves were selected for each outcome of interest.

RESULTS

For ovulation induction with IUI, fresh ET, FET, and spontaneous conception, the slope analysis of growth curves for per-week growth rate of HC, AC, HC/AC ratio, and EFW demonstrated no difference. A subgroup analysis of fresh ET and FET groups, for same outcomes, also showed no difference.

CONCLUSION

These findings contribute to the very limited literature on fetal growth trajectories following infertility treatment and suggest no significant differences in fetal growth for ovulation induction with IUI, fresh ET, FET, and spontaneous conception following infertility. It is possible there were no differences in growth trajectories between these conception methods because the majority of children born following infertility are of normal birth weight. While results are reassuring, further research with larger populations is warranted.

Developmental Plasticity in Response to Embryo Cryopreservation: The Importance of the Vitrification Device in Rabbits

Simple Summary

This study was conducted to demonstrate how embryo manipulation techniques incur phenotypic changes throughout life. This study reports the first evidence demonstrating that the vitrification device used is not a trivial decision, providing valuable information about how the cooling–warming rates during vitrification can be partly responsible of the postnatal phenotypic variations.

Abstract

In this study, we evaluated the effect of embryo vitrification using two different devices on adulthood phenotype in rabbits. In vitro development, prenatal embryo survival, body weight, growth performance, haematological and biochemical peripheral blood analysis, reproductive performance, and lactation performance traits were compared between the experimental groups. They derived from naturally-conceived embryos (NC), fresh-transferred embryos (FT), vitrified-transferred embryos using mini-straw (VTs), or vitrified-transferred embryos using Cryotop (VTc). Straw-vitrified embryos exhibited lower in vitro developmental rates and in vivo survival rates following embryo transfer compared to its Cryotop-vitrified counterparts. Moreover, the VTs group exhibited higher foetal losses than VTc, FT, and NC groups. Independently of the vitrification device, vitrified-transferred (VT) offspring showed a skewed sex ratio in favour of males, and an increased birth bodyweight. In contrast, postnatal daily growth was diminished in all ART (i.e., FT and VT) animals. In adulthood, significant differences in body weight between all groups was founded—all ART progenies weighed less than NC animals and, within ART, VT animals weighed less than FT. For VT groups, weight at adulthood was higher for the VTs group compared with the VTc group. Peripheral blood parameters ranged between common values. Moreover, no differences were found in the fertility rates between experimental groups. Furthermore, similar pregnancy rates, litter sizes, and the number of liveborns were observed, regardless of the experimental group. However, decreased milk yield occurred for VTc and FT animals compared to VTs and NC animals. A similar trend was observed for the milk composition of dry matter and fat. Concordantly, reduced body weight was found for suckling kits in the VTc and FT groups compared to VTs and NC animals. Our findings reveal that developmental changes after the embryo vitrification procedure could be associated with an exhibition of the embryonic developmental plasticity. Moreover, to our best knowledge, this study reports the first evidence demonstrating that the vitrification device used is not a trivial decision, providing valuable information about how the cooling–warming rates during vitrification can be partly responsible of the postnatal phenotypic variations.

Maternal and perinatal outcomes in programmed versus natural vitrified-warmed blastocyst transfer cycles

RESEARCH QUESTION

Do maternal and perinatal outcomes differ between natural and programmed frozen embryo transfer (FET) cycles?

DESIGN

Retrospective cohort study at a university-affiliated fertility centre including 775 patients who underwent programmed or natural FET cycles resulting in a singleton live birth using blastocysts vitrified between 2013 and 2018.

RESULTS

A total of 384 natural and 391 programmed FET singleton pregnancies were analysed. Programmed FET resulted in higher overall maternal complications (32.2% [126/391] versus 18.8% [72/384]; P < 0.01), including higher probability of hypertensive disorders of pregnancy (HDP) (15.3% [60/391] versus 6.3% [24/384]; P < 0.01), preterm premature rupture of membranes (2.6% [10/391] versus 0.3% [1/384]; P = 0.02) and caesarean delivery (53.2% [206/387] versus 42.8% [163/381]; P = 0.03) compared with natural FET. After controlling for potential confounders, including age, body mass index, parity, smoking status, history of diabetes or chronic hypertension, infertility diagnosis, number of embryos transferred and use of preimplantation genetic testing, the adjusted odds ratio for HDP was 2.39 (95% CI 1.37 to 4.17) and for overall maternal complications was 2.21 (95% CI 1.51 to 3.22) comparing programmed with natural FET groups. The groups did not significantly differ for any perinatal outcomes analysed, including birth weight (3357.9 ± 671.6 g versus 3318.4 ± 616.2 g; P = 0.40) or rate of birth defects (1.5% [6/391] versus 2.1% [8/384]; P = 0.57), respectively.

CONCLUSION

Vitrified-warmed blastocyst transfer in a programmed cycle resulted in a twofold higher probability of HDP compared with transfer in a natural cycle. Natural FET cycle should, therefore, be recommended as first line for all eligible patients undergoing FET to reduce the risk of HDP.

Increased blood pressure and impaired endothelial function after accelerated growth in IVF/ICSI children

STUDY QUESTION

What is the effect of growth velocity (height and weight) in early infancy on metabolic end-points and endothelial function in children born after ART?

SUMMARY ANSWER

Neonatal, infant and childhood growth is positively related to blood pressure in 9-year-old IVF/ICSI offspring, while growth in childhood was negatively associated with endothelial function.

WHAT IS KNOWN ALREADY

Offspring of pregnancies conceived after ART are at risk for later cardiometabolic risk factors. It is well established that early growth is related to numerous later cardiometabolic risk factors such as high blood pressure. This concept is known as the Developmental Origin of Health and Disease theory.

STUDY DESIGN SIZE DURATION

The relation between early growth and later cardiometabolic risk profile was studied in the MEDIUM-KIDS study, a prospective observational cohort study in children born after an IVF/ICSI treatment. In 131 children (48.1% males) at the average age of 9.4 years, cardiometabolic outcomes were assessed and growth data from birth until age 9 years were collected from child welfare centers.

PARTICIPANTS/MATERIALS SETTINGS METHODS

The following cardiometabolic outcomes were assessed: blood pressure, skinfolds, lipid spectrum, hair cortisone and glucose and insulin levels. Data on maximum skin perfusion after transdermal delivery of acetylcholine as a measure of endothelial function were collected.Growth charts were obtained electronically from child welfare centers, which offer free consultations and vaccinations to all Dutch children. At these centers, height and weight are recorded at predefined ages. Growth was defined as z-score difference in weight between two time points. Multivariable linear regression analysis was used to model the relation between growth and cardiometabolic outcomes. The following growth windows were -studied simultaneously in each model: 0-1 month, 1-3 months, 3-6 months, 6-11 months, 11-24 months and 2-6 years. The model was adjusted for height growth in all intervals except for 0-1 month.

MAIN RESULTS AND THE ROLE OF CHANCE

In multivariable linear regression analyses, multiple growth windows were positively associated with blood pressure, for example growth from 2-6 years was significantly related to systolic blood pressure: B = 4.13, P = 0.005. Maximum skin perfusion after acetylcholine was negatively associated with height-adjusted weight gain from 2 to 6 years: B = -0.09 (log scale), P = 0.03. Several growth windows (weight 1-3 months, 3-6 months, 6-11 months, 11-24 months, 2-6 years) were positively linked with total adiposity. Lipids, glucose tolerance indices and cortisone were not related to growth.

LIMITATIONS REASONS FOR CAUTION

This study is of modest size and of observational nature, and we did not include a control group. Therefore, we cannot assess whether the observed associations are causal. It is also not possible to analyze if our observations are specific for, or exacerbated in, the ART population. Ideally, a control group of naturally conceived siblings of IVF/ICSI children should simultaneously be studied to address this limitation and to assess the impact of the ART procedure without the influence of parental (subfertility) characteristics.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study contribute to our understanding of the reported increased risk for hypertension in ART offspring. We speculate that early, accelerated growth may be involved in the reported increased risk for hypertension in ART offspring, with endothelial dysfunction as a possible underlying mechanism. However, additional research into the mechanisms involved is required.

STUDY FUNDING/COMPETING INTERESTS

The study was financially supported by the March of Dimes, grant number #6-FY13-153. The sponsor of the study had no role in study design, data collection, data analysis, data interpretation or writing of the paper. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

NTR4220.

The Future of Cryopreservation in Assisted Reproductive Technologies

Societal changes and the increasing desire and opportunity to preserve fertility have increased the demand for effective assisted reproductive technologies (ART) and have increased the range of scenarios in which ART is now used. In recent years, the "freeze-all" strategy of cryopreserving all oocytes or good quality embryos produced in an IVF cycle to transfer later-at a time that is more appropriate for reasons of medical need, efficacy, or desirability-has emerged as an accepted and valuable alternative to fresh embryo transfer. Indeed, improvements in cryopreservation techniques (vitrification) and the development of more efficient ovarian stimulation protocols have facilitated a dramatic increase in the practice of elective frozen embryo transfer (eFET). Alongside these advances, debate continues about whether eFET should be a standard treatment option available to the whole IVF population or if it is important to identify patient subgroups who are most likely to benefit from such an approach. Achieving successful outcomes in ART, whether by fresh or frozen embryo transfer, is influenced by a wide range of factors. As well as the efficiency of IVF and embryo transfer protocols and techniques, factors affecting implantation include maternal aging, sperm quality, the vaginal and endometrial microbiome, and peri-implantation levels of serum progesterone. The safety of eFET, both during ART cycles and on longer-term obstetric and neonatal outcomes, is also an important consideration. In this review, we explore the benefits and risks of freeze-all strategies in different scenarios. We review available evidence on the outcomes achieved with elective cryopreservation strategies and practices and how these compare with more traditional IVF cycles with fresh embryo transfers, both in the general IVF population and in subgroups of special interest. In addition, we consider how to optimize and individualize "freeze-all" procedures to achieve successful reproductive outcomes.

Is Embryo Cryopreservation Causing Macrosomia-and What Else?

The number of embryos transferred during an IVF cycle is directly related to the high incidence of multiple births, which is the culprit of perinatal morbidity. Therefore, single fresh embryo transfer (ET) strategy, or freeze-all, followed by a single frozen-thawed embryo transfer (FET) cycle, may dramatically reduce the rate of multiple births, without compromising the cumulative live birth rates (LBRs). A literature review was conducted for all available evidences assessing obstetrics and perinatal outcomes associated with FET compared to fresh ET and natural conception. While studies comparing fresh and FET cycles in normal responders have yielded conflicting results for pregnancy rate, FET was associated with lower risk of prematurity and low birth weight and increased risk of large for gestational age (LGA) and/or macrosomic in singletons, when compared with fresh ET. Macrosomic/LGA births have a higher risk of fetal hypoxia, stillbirth, shoulder dystocia, perineal lacerations, cesarean section, postpartum hemorrhage and neonatal metabolic disturbances at birth. Nonetheless, it seems that other than higher risk of fetal macrosomia, there are additional obstetric complications associated with FET. The relative risk of hypertensive disorders in pregnancy, as well as perinatal mortality were also demonstrated to be increased in FET compared with singletons from fresh ET and natural conception. Therefore, when considering elective freeze-all policy, in addition to LBR and the risk of ovarian hyperstimulation syndrome, physicians should consider the aforementioned increased FET cycles' pregnancy complications, including LGA/ macrosomia, hypertensive disorders of pregnancy, as well as perinatal mortality.

Risk of Lower Birth Weight and Shorter Gestation in Oocyte Donation Pregnancies Compared With Other Assisted Reproductive Technology Methods: Systematic Review

OBJECTIVE

Oocyte donation (OD) is associated with an increased risk of pregnancy-induced hypertension, but the evidence of an association between OD and infant outcomes, including birth weight and gestational age, is conflicting. This study sought to determine the associations between oocyte donation and birth weight or gestational age compared with other forms of autologous oocyte assisted reproductive technology (ART).

METHODS

Medline, Embase, and the CENTRAL Trials Registry of the Cochrane Collaboration were searched using a comprehensive search strategy. Studies of women over 24 weeks gestation compared infant outcomes among OD pregnancies versus other ART. Study quality was assessed, and a meta-analysis of mean birth weight and gestational age was conducted using a random effects model.

RESULTS

Nineteen studies were included. Four studies showed a significant association between OD and lower birth weights, and five studies found significant differences in gestational age between OD and autologous oocyte ART. The pooled difference in birth weight means between OD and autologous ART was -42 (-88, 4) . The pooled difference in gestational age was -0.4 weeks (-0.8, 0.0 weeks).

CONCLUSION

A high degree of interstudy heterogeneity exists, and the association between OD and infant outcomes remains unclear.

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.

Birthweight difference of singletons conceived through in vitro fertilization with frozen versus fresh embryo transfer: An analysis of 5406 embryo transfers in a retrospective study 2013-2018

INTRODUCTION

Perinatal risks after frozen embro transfer (FET) have been reassuring but some authors suggest that birthweights are higher after FET than after fresh embryo transfer (ET). The primary objective of this retrospective study, conducted in Clinique de la Sagesse, Rennes (France) from December 2013 to March 2017, was to determine whether a difference in birthweight exists between children conceived through in vitro fertilization (IVF) with frozen versus fresh ET. The secondary objective was to compare live birth rates after frozen versus fresh cycles.

MATERIAL AND METHODS

All couples undergoing IVF were included. Cycles with gamete donation and twin pregnancies were excluded. Hormone therapy was used in all embryo transfers. The main outcome measures were the child's birthweight, mode of delivery, gestation length and sex, maternal characteristics, and IVF characteristics. The primary endpoint was birthweight.

RESULTS

We studied 5406 embryo transfers and the 708 resulting singleton live births on which birthweight data were available. Mean birthweight was 3357g after frozen embryo transfer versus 3183g after fresh embryo transfer (p<0.001). After adjusting for confounding factors, the children born after frozen embryo transfer were 165.2g heavier (95%CI [92.96-237.51]). No difference was found in gestation length. Live birth was obtained after the 1.6th IVF attempt. Live birth rate was higher for fresh cycles (19% versus 12%, p<0.001), and the caesarean rate lower (16% versus 21%).

DISCUSSION

Birthweight was higher after frozen embryo transfer for a similar gestational age. Further research is needed to elucidate the mechanisms responsible for this difference.

Risk of adverse perinatal outcomes after oocyte donation: a systematic review and meta-analysis

RESEARCH QUESTION

In women with singleton pregnancies conceived after assisted reproductive technologies, does the in vitro fertilization with oocyte donation (IVF-OD) affect the perinatal and maternal outcomes compared to autologous in vitro fertilization (IVF-AO)?

DESIGN

Systematic review and meta-analysis of studies comparing perinatal and maternal outcomes in singleton pregnancies resulting from IVF-OD versus IVF-AO. An electronic literature search in Pubmed, MEDLINE, and Cochrane database was performed. The main outcome measures were hypertensive disorders in pregnancy, preeclampsia, severe preeclampsia, pregnancy-induced hypertension, preterm birth, early preterm birth, low birth weight, and very low birth weight.

RESULTS

Twenty-three studies were included. IVF-OD is associated with a higher risk of hypertensive disorders in pregnancy (OR 2.63, 2.17-3.18), preeclampsia (OR 2.64; 2.29-3.04), severe preeclampsia (OR 3.22; 2.30-4.49), pregnancy-induced hypertension (OR 2.16; 1.79-2.62), preterm birth (OR 1.57; 1.33-1.86), early preterm birth (OR 1.80; 1.51-2.15), low birth weight (OR 1.25, 1.20-1.30), very low birth weight (OR 1.37, 1.22-1.54), gestational diabetes (OR 1.27; 1.03-1.56), and cesarean section (OR 2.28; 2.14-2.42). There was no significant difference in the risk of preterm birth or low birth weight when adjusted for preeclampsia.

CONCLUSIONS

IVF-OD patients should be considered an independent risk factor for some adverse perinatal outcomes, mainly hypertensive disorders in pregnancy, preeclampsia, and severe preeclampsia. Immunological and hormonal aspects may be involved in these results, and further research focusing in the etiopathogenesis of these pathologies are needed.

Associations between estimated foetal weight discordance and clinical characteristics within dichorionic twins: The NICHD Fetal Growth Studies

BACKGROUND

Birthweight discordance is well studied, with less known about longitudinal inter-twin differences in foetal growth.

OBJECTIVE

To examine inter-twin per cent differences in EFW (EFW_% ), head (HC_% ) and abdominal circumference (AC_% ), and femur length (FL_% ) across gestation in dichorionic twin gestations and explore associated characteristics.

METHODS

Foetal biometrics were assessed by ultrasound and EFW calculated at ≤6 study visits among women with dichorionic twin pregnancies enrolled in the NICHD Fetal Growth Studies cohort (US, 2012-2013). Inter-twin per cent difference was defined: ([Size_{larger twin}  - Size_{smaller twin} ]/Size_{larger twin}  × 100). Linear mixed models evaluated per cent differences in foetal biometrics at 15 weeks and their change per week overall and by maternal/neonatal characteristics in unadjusted and adjusted models.

RESULTS

In 140 pregnancies, inter-twin per cent differences increased across gestation for EFW (0.18%/week, 95% confidence interval [CI] 0.10, 0.27), HC (0.03%/week, 95% CI 0.00, 0.06), and AC (0.03%/week, 95%CI -0.01, 0.08) but decreased for FL (-0.03%/week, 95% CI -0.09, 0.02). After adjustment, change in EFW_% difference across gestation differed by pre-pregnancy body mass index (BMI [kg/m² ]; underweight [<18.5]; normal weight [18.5-24.9]; overweight [25.0-29.9]; obese [≥30.0]; P_interaction  = .022); and conception method (in vitro fertilisation [IVF], intrauterine insemination, ovulation induction medication, donor egg/embryo, none; P_interaction  = .060). While EFW_% difference increased with normal pre-pregnancy BMI (0.24%/week, 95% CI 0.12, 0.37), little change was noted with pre-pregnancy obesity (0.01%/week, 95% CI -0.15, 0.17). EFW_% difference increased in conceptions without fertility treatments (0.23%/week, 95% CI 0.11, 0.34) but not IVF conceptions (-0.00%/week, 95% CI -0.16, 0.16). Similar patterns of differences across gestation were noted for HC_% by conception method (P_interaction  = .026) and AC_% by pre-pregnancy BMI (P_interaction  = .071); changes in HC_% differed by parity (nulliparous, multiparous; P_interaction  = .004).

CONCLUSIONS

EFW_% difference increased across gestation in dichorionic twins, but remained stable with pre-pregnancy obesity or IVF conception, patterns mirrored for HC and AC. Research is needed to understand pathologic versus physiologic differential twin growth trajectories.

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.

Is a woman's chronological age or 'ovarian age' more important in determining perinatal outcome after assisted reproductive treatment?

Ovarian reserve (OR) decreases as women get older but there is considerable variation in the rate at which this occurs. Older women are at increased risk of complications during pregnancy. The aim of the study was to determine whether poor OR influences perinatal outcomes independent of age. All fresh IVF/ICSI cycles in which a single embryo was transferred between 1 January 2010 and 31 December 2016 were reviewed. An anti-Müllerian hormone (AMH) concentration of ≤5.4 pmol/l was considered poor and 5.41-24.99 pmol/l normal. Data were collected regarding cycle outcome, congenital anomalies, gestational age at delivery and birth weight. A total of 1520 women were included, of whom 1197 had normal OR and the remaining 323 had poor OR. Once pregnant, after adjusting for maternal age, women with poor OR (n = 109) were no more likely to experience a biochemical pregnancy or miscarriage (41.3% versus 41.6%, p = 0.809) than women with normal OR (n = 596). There were no significant differences in rates of congenital anomalies (1.8% versus 1.2%, p = 0.636), birth weight (3272 ± 630.7 g versus 3376.4 ± 576.3 g, p = 0.216) or gestational age at delivery (38.9 ± 2.3 weeks versus 39.1 ± 2.1 weeks, p = 0.517) between women with normal or poor OR. OR does not appear to affect pregnancy loss rates, incidence of congenital anomalies, birth weight, or gestational age at delivery after adjusting for maternal age.

The impact of using donor sperm in assisted reproductive technology cycles on perinatal outcomes

OBJECTIVE

To assess the impact of using donor sperm in assisted reproductive technology (ART) cycles on perinatal outcomes.

DESIGN

Historical cohort study.

SETTING

US national database from the Society of Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) from 2012 to 2013.

PATIENT(S)

Patients undergoing the first fresh autologous ART cycle using either donor or partner sperm.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Miscarriage, preterm birth, low birthweight rates.

RESULTS

A total of 134,710 fresh autologous ART cycles were evaluated from the SART CORS database. Following exclusion criteria and after restricting to the first cycle, 2,123 donor sperm and 42,799 partner sperm ART cycles were included in the final analyses. After adjusting for all confounding variables (including maternal age, race, body mass index, smoking status, gravidity, history of preterm birth, highest follicle stimulating hormone count, blastocyst transfer percentage, total embryo transferred, and etiology of infertility), no statistically significant differences in miscarriage rates, preterm births, very preterm births, low birthweight, and very low birthweight were observed. Birthweight was significantly lower in the partner sperm group than in the donor sperm group (3,292 ± 601 and 3,233 ± 592 g in donor and partner sperm groups, respectively, adjusted P value 0.003); however, this small absolute difference (adjusted effect estimate 42 g, 95% CI 14.7-70.9) does not carry clinical significance.

CONCLUSIONS

The use of donor sperm in fresh autologous ART cycles was not associated with increased miscarriage, preterm births, or low birthweights, as compared to cycles using partner sperm. This information can be used in patient counseling to reassure patients using donor sperm in ART cycles.

Increased pregnancy complications following frozen-thawed embryo transfer during an artificial cycle

PURPOSE

This study aimed to clarify the risks of adverse pregnancy outcomes in patients and their offspring after frozen embryo transfer (FET) during an artificial cycle (AC).

METHODS

We conducted a retrospective cohort study that included all FET cycles and subsequent deliveries in a single centre between August 2013 and March 2016. Pregnancy, obstetric and neonatal outcomes were compared among patients treated during an AC or a natural cycle with luteal phase support (NC-LPS). Multivariate logistic regression was performed to evaluate the relationship between endometrial preparation schemes and pregnancy, obstetric and neonatal outcomes.

RESULTS

AC-FET was not a significant risk factor for clinical pregnancy rate, multiple birth rate or miscarriage rate after adjusting for potential confounders. However, AC-FET was a significant risk factor for ectopic pregnancy rate (adjusted odds ratio (AOR), 1.738; 95% confidence interval (CI), 1.086-2.781) and live birth rate (AOR, 0.709; 95% CI, 0.626-0.802). Regarding obstetric outcomes, AC-FET was found to be associated with an increased risk for hypertension disorder (AOR, 1.780; 95% CI, 1.262-2.510) and caesarean section (AOR, 1.507; 95% CI, 1.195-1.900). In multiples, birth weight (2550 g (2150-2900 g) in AC-FET vs. 2600 g (2350-2900 g) in NC-LPS; P = 0.023), gestational age (36.6 weeks (35.3-37.6 weeks) vs. 37.1 weeks (36.1-37.9 weeks); P < 0.001), and z-score (- 0.5 (- 1.1, - 0.0) vs. - 0.4 (- 1.0, 0.2); P = 0.009) were higher in the NC-LPS group than in the AC-FET group, although there were no differences in these variables among singletons.

CONCLUSION

Compared with NC-LPS, AC-FET seemed to have a negative effect on obstetric outcomes.

Risk of ischemic placental disease in fresh and frozen embryo transfer cycles

OBJECTIVES

To evaluate the association of fresh and frozen embryo transfer with the development of ischemic placental disease (IPD), hypothesizing that differences in implantation environment affect placentation and thus pregnancy outcomes.

DESIGN

We performed a secondary analysis of a retrospective cohort study of deliveries linked to IVF cycles.

SETTING

Tertiary hospital and infertility treatment center.

PATIENT(S)

We included all women who underwent an autologous IVF cycle and had a live-born infant or an intrauterine fetal demise (IUFD). We excluded women less than 18 years of age.

INTERVENTION(S)

We compared pregnancies resulting from frozen embryo transfer (frozen) cycles with those resulting from fresh embryo transfer (fresh) cycles.

MAIN OUTCOME MEASURE(S)

The primary outcome was a composite outcome of IPD or IUFD due to placental insufficiency. Ischemic placental disease included pre-eclampsia, placental abruption, and small for gestational age (SGA). We calculated risk ratios (RRs) and 95% confidence intervals (CIs).

RESULT(S)

Compared with fresh cycles, frozen cycles had a lower risk of IPD or IUFD from placental insufficiency (RR 0.75, 95% CI 0.59-0.97). Frozen cycles also conferred a lower risk of SGA than fresh cycles (RR 0.58, 95% CI 0.41-0.81). Risks of pre-eclampsia (RR 1.3, 95% CI 0.84-1.9) and abruption (RR 1.2, 95% CI 0.56-2.4) were similar.

CONCLUSION(S)

There was a lower risk of IPD among frozen cycles compared with fresh cycles. This association was largely driven by lower risk of SGA among frozen cycles.

Pregnancy rates after pre-implantation genetic screening for aneuploidy are only superior when trophectoderm biopsy is performed on hatching embryos

PURPOSE

In vitro fertilization with trophectoderm embryo biopsy and pre-implantation genetic screening with comprehensive chromosomal screening (PGS-CCS) for aneuploidy is becoming increasingly more popular. Embryos are cryopreserved and implanted in a subsequent frozen thawed embryo transfer cycle (FET). No studies have investigated differences in pregnancy outcomes by timing of trophectoderm biopsy relative to stages of blastocyst development.

METHODS

Retrospective study of all patients (n = 363) at a single IVF center between January 1, 2013 and December 31, 2016 undergoing single embryo transfer with PGS-CCS where embryos were cryopreserved with subsequent FET. Embryo expansion and grading was assessed both at the time of biopsy and transfer. Pregnancy rates were analyzed by embryo expansion and embryo grading.

RESULTS

Implantation, clinical pregnancy, and live birth rates improved significantly with increased embryo expansion at the time of embryo biopsy (P < 0.001). Pregnancy loss decreased with increases in embryo expansion prior to biopsy (P < 0.001). Superior live birth rates with PGS-CCS were seen when embryos were hatching at the time of biopsy (p < 0.001). For fresh and frozen embryo transfers without PGS-CCS, embryo expansion did not affect pregnancy outcomes.

CONCLUSIONS

PGS-CCS significantly increases implantation and live birth rates only if embryos are hatching at the time of biopsy. The embryo biopsy itself on a non-hatching embryo significantly damages the embryo in ways which are not reflected in future embryo expansion. IVF labs should wait until embryos hatch before performing trophectoderm biopsy.

High implantation and clinical pregnancy rates with single vitrified-warmed blastocyst transfer and optional aneuploidy testing for all patients

This study reports the results of a 2-year long IVF programme ('One by One') in which all patients (median age 40 years; range 27-45 years) were offered preimplantation genetic testing for aneuploidy (PGT-A) and had all blastocysts vitrified (freeze-only), followed later by single vitrified-warmed blastocyst transfer (vSET) in managed cycles. Between January 2016 and December 2017, a total of 155 patients started 222 treatment cycles and 99 (45%) cycles resulted in one or more vitrified blastocysts (untested or with normal copy number for all chromosomes) available for transfer. Seventeen patients (11%) aged ≤35 years opted out of PGT-A. Over this period, 85 vSETs in 74 patients resulted in an implantation rate of 80% (68/85) and a singleton clinical pregnancy rate of 66% (56/85). Cumulative live birth rates will not be known for 1-2 years. Nevertheless, these high success rates with vSET confirm larger studies using selected patients and are likely to deliver similar, if not higher, live birth rates per cycle started than rates typically reported in national registries with conventional IVF and transfer of one or more fresh and/or frozen embryos.

Fertility and Neonatal Outcomes of Freeze-All vs. Fresh Embryo Transfer in Women With Advanced Endometriosis

Background: Eutopic endometrium from women with endometriosis has functional changes in several aspects, which may largely account for the decrease in the quality of endometrial receptivity. It is of utmost importance to know whether freeze-all strategy can restore optimal receptivity in endometriotic women leading to the better ART outcomes. Methods: Retrospective study involved patients with advanced endometriosis undergoing first embryo transfer cycles during the period from March 2006 to March 2017 at a tertiary care center. After propensity score matching, there were 506 women in the freeze-all group and 255 women in fresh group. Our main outcomes included the rates of implantation, clinical pregnancy, and live birth. Subgroup analyses were performed after stratification by the number of oocytes retrieved and fertilization method. Neonatal outcomes included gestational age and birth weight z-score for singletons and multiple births. Results: In our matched cohort, the implantation, clinical pregnancy and live birth rates were statistically significantly higher in the freeze-all group compared with fresh transfer groups (34.4 vs. 25.5%, 51.8 vs. 38.8%, and 45.3 vs. 31.8%, all P < 0.001, respectively). A more beneficial effect of freeze-all cycles was found in patients who got more than 15 oocytes. Additionally, when ICSI insemination techniques were used to achieve fertilization, the advantage of freeze-all strategy was not obvious. Assessment of 382 babies showed no statistically significant difference in the mode of delivery, sex of live-born, gestational age, unadjusted median birth weight, and z-score between two study groups. Conclusion: Freeze-all strategy is an attractive option to improve the outcomes of ART for women with advanced endometriosis.

Comparison of perinatal outcomes following frozen embryo transfer cycles using autologous versus donor oocytes in women 40 to 43 years old: analysis of SART CORS data

OBJECTIVE

To study the differences in perinatal outcomes after frozen embryo transfer cycles using autologous or donor oocytes in women of advanced maternal age.

DESIGN

Historical cohort study.

SETTING

US national database from the Society of Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) from 2009 to 2013.

PATIENT(S)

Women at 40-43 years of age undergoing autologous frozen embryo transfers (a-FET) or donor oocyte frozen embryo transfers (d-FET) resulting in singleton pregnancies that were entered in the SART CORS database from 2009 to 2013.

RESULTS

a-FET resulted in 4402 singleton live births whereas d-FET resulted in 2703 singleton live births. d-FET resulted in a higher risk of preterm births (< 37 weeks), with adjusted odds ratio (aOR) 1.33 (95% CI 1.02-1.75), but similar risk of small for gestational age (SGA), with aOR 1.75 (95% CI 0.85-3.7), when compared to a-FET. However, when only single blastocyst transfer cycles are considered, d-FET and a-FET showed no difference in preterm births or other adverse perinatal outcomes.

CONCLUSIONS

Singletons resulting from d-FET are at increased risk for perinatal morbidity. However, the risk was diminished in single blastocyst transfer cycles. Our study supports the current American Society for Reproductive Medicine (ASRM) guidelines of transferring a single blastocyst in d-FET cycles.

Improved outcomes after blastocyst-stage frozen-thawed embryo transfers compared with cleavage stage: a Society for Assisted Reproductive Technologies Clinical Outcomes Reporting System study

OBJECTIVE

To investigate whether there is a difference in obstetrical and perinatal outcomes in blastocyst frozen-thawed embryo transfers (FETs) compared with cleavage-stage FET.

DESIGN

A retrospective cohort study.

SETTING

Not applicable.

PATIENT(S)

Women undergoing autologous FETs at either the blastocyst stage (n = 118,572) or the cleavage stage (n = 117,619) reported to the Society for Assisted Reproductive Technology in the years 2004-2013.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth, gestational age, birth weight, miscarriage.

RESULT(S)

After controlling for confounders, there were a 49% increased odds of live birth after blastocyst-stage FET compared with cleavage-stage FET (odds ratio [OR] = 1.49; 95% confidence interval [CI], 1.44, 1.54). Additionally, blastocyst FET was associated with a 68% (OR = 1.68; 95% CI, 1.63, 1.74) increased odds of clinical pregnancy and an 7% (OR = 0.93; 95% CI, 0.88, 0.92) decreased odds of miscarriage. There was also a 16% increased odds of preterm delivery (OR = 1.16; 95% CI, 1.06, 1.27) after blastocyst FET but no difference in birth weights.

CONCLUSION(S)

In patients undergoing FET, blastocyst-stage transfer is associated with higher live-birth rates when compared with cleavage-stage transfers. Furthermore, perinatal outcomes are similar between the groups.

Retrospective Study to Compare Frozen-Thawed Embryo Transfer with Fresh Embryo Transfer on Pregnancy Outcome Following Intracytoplasmic Sperm Injection for Male Infertility

BACKGROUND With the development of assisted reproductive technology, there is increasing evidence that frozen-thawed (FT) embryo transfer achieves a better outcome when compared with fresh embryo transfer in different types of infertile individuals. This aim of this study was to investigate the effect of FT embryo transfer for intracytoplasmic sperm injection (ICSI) on pregnancy outcome in assisted reproductive technology for male infertility. MATERIAL AND METHODS A total of 516 embryo transfer cycles (286 fresh embryo transfer cycles and 230 FT embryo transfer cycles) were studied, in which ICSI treatment was performed for the first time because of male infertility. The women in the study were normal or had Fallopian tube abnormalities. The clinical data and pregnancy outcomes of these two study groups were compared. RESULTS The implantation rate, pregnancy rate, and multiple birth rate of the FT embryo transfer group were similar when compared with the fresh embryo transfer group. The live birth rate of the FT embryo transfer group was significantly greater when compared with the fresh embryo transfer group (P<0.05). The rate of miscarriage of the FT embryo transfer group was 6.52%, which was significantly less than that of the fresh embryo transfer group (14.01%) (P<0.05). The gestational age and neonatal birth weight were not significantly different between the two groups (P>0.05). CONCLUSIONS FT embryo transfer was an effective and safe treatment for patients undergoing ICSI, which improved the live birth rate and reduced the rate of miscarriage.

[Culture conditions for gametes and embryos: Which culture medium? Which impact on newborn?]

Many studies have examined the impact of cell/embryo culture media on the development of human embryo during IVF process, but few studies have followed up and compared the effects of these culture media on the developmental outcome of children conceived by IVF. As recurrent experimental evidence from animal studies suggests potential long-term effects of embryo culture media on the health outcome of IVF-conceived children, more studies are needed to clarify the role of the culture media and mechanisms underlying such effects. In human, however, the effects of culture media are difficult to pinpoint due to complications stem from both the influence of maternal nutrition during the gestational period and the parental genetic. Based on a simple review of the literature integrating animal experimentations and human clinic studies, we suggest that the composition of culture medium should be considered beyond the character of unique or sequential medium, corresponding to "let embryo choose" or "back to nature" respectively. Instead, we suggest that the main components of embryo culture media should be considered from the point of view of metabolic consequences and potential epigenetic effects. Given that energetic metabolites can regulate epigenetic machinery, we hypothesize that metabolic abnormalities linked to morphological abnormalities could reveal epigenetic defects in embryos.

[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.