Impact of blastocyst transfer on offspring sex ratio and the monozygotic twinning rate: a systematic review and meta-analysis

Sex ratio shift after frozen single blastocyst transfer in relation to blastocyst morphology parameters

The sex ratio shift was observed in peoples who underwent ART treatment. Moreover, there is limited evidence on differences in sex ratio between single frozen-thawed blastocyst morphology, insemination type and transfer days. So further research is needed in this area with regard to factors possibly affecting the sex ratio. Retrospective study based on multicenter including two large assisted reproduction centers in Shanghai and Wuhan in China. A total of 6361 singleton delivery offspring after frozen-thawed blastocyst transfer. Propensity score weighting and logistic regression models were used to estimate the associations between blastocyst morphology grading and child sex ratio. The main outcome measures is singleton sex ratio. In our study, the primary outcome measure was sex ratio which was calculated as the proportion of male newborns among all live births. Higher quality blastocysts resulted in a higher sex ratio than single poor-quality frozen-thawed blastocyst transfer. Among the three blastocyst morphological parameters of trophectoderm (TE), Grade A and B were significantly associated with a higher sex ratio than Grade C. The similar trend was observed in both IVF and ICSI treated subgroups. As compared with expansion (4 + 3), expansion degree 6 achieved a higher sex ratio in overall populations and IVF treated subgroup. Transferring blastocysts of day 6 had the highest sex ratio both in IVF group and ICSI group. A 6.95% higher sex ratio in transferring blastocysts of day 5 in IVF group than those in ICSI group. No significant association between inner cell mass degree and sex ratio was observed. However, as compared with IVF treatment, all morphology parameters achieved the similar or the biased sex ratio favoring female in ICSI treated subgroup. Quality of blastocysts was positively associated with sex ratio. TE score and expansion degree rather than ICM were significantly associated with sex ratio at birth. ICSI treatment promotes the biased sex ratio favoring female.

Which transfer day results in the highest live birth rate for PCOS patients undergoing in vitro fertilization?

BACKGROUND

Polycystic ovary syndrome (PCOS) has unusual levels of hormones. The hormone receptors in the endometrium have a hostile effect and make the microenvironment unfavorable for embryo implantation. The use of gonadotropin stimulation during in vitro fertilization (IVF) may have an impact on embryo implantation and live birth rate. According to recent data, the clinical results of day 4 embryo transfer (D4 transfer) were on par with those of day 5 embryo transfer (D5 transfer) in IVF-ET. There are few studies comparing the outcomes of transplants with various etiologies and days. The purpose of this study was to determine which transfer day had the best result for PCOS patients undergoing IVF.

METHODS

This retrospective cohort study was conducted in the Xingtai Infertility Specialist Hospital between January 2017 and November 2021. A total of 1,664 fresh ART cycles met inclusion criteria, including 242 PCOS transfers and 1422 tubal factor infertility transfers.

CONCLUSIONS

PCOS individuals had the highest live birth rate on D4 transferred. It was not need to culture embryos to blastocysts to optimize embryo transfer for PCOS women. This could be a novel approach to transplantation for PCOS.

Effect of blastocyst quality on human sex ratio at birth in a single blastocyst frozen thawed embryo transfer cycle

RESEARCH QUESTION

To determine whether blastocyst quality affects the sex ratio at birth through a single blastocyst frozen - thawed embryo transfer (SBFET) cycle.

DESIGN

In this retrospective analysis, we examined 3,041 singleton infants born following SBFET between 2017 and 2020 at a single institution. We compared the sex ratios of these infants with respect to the blastocyst quality, embryo growth rate, and morphology.

RESULTS

The main outcomes of this study were that the sex ratio (M/F) at birth of SBFET was 1.24. Mothers >40 years old had a considerably lower sex ratio than mothers <40 years old (0.39 vs. 1.23-1.28, p < .05). Transplanting high-quality blastocysts significantly increased the proportion of boys born (1.29 vs. 0.88, p < .05). There were no significant differences in the sex ratio with respect to the inner cell mass (ICM) score and expansion degree. Additionally, a high trophoblastic cell (TE) score resulted in a significantly higher sex ratio than the TE score with C (1.62 vs. 1.15 vs. 0.85, p < .001). Multivariable logistic regression analysis was performed to determine which variables were significant factors affecting sex ratio, and the outcomes were consistent with previous findings.

CONCLUSIONS

Our study indicated that high-quality, especially good TE score, had a higher chance of resulting in a male infant than a female infant.

Is there a relationship between morphokinetic parameters and neonatal sex in fresh embryo transfers?

To investigate whether morphokinetic parameters differ between male and female embryos in IVF embryos resulting in live births, a retrospective cohort study was undertaken. Files of all live births resulting from a single embryo transfer (SET) cultured in time-lapse incubators between 2013 and 2019 in two tertiary care centres were reviewed. The study group consisted of 187 SETs resulted in 187 live births, of which 100 were females (53.5%) and 87 were males (46.5%). Embryo selection for transfer was based on the known implantation data (KID) score provided by the Embryoscope and morphological assessment by experienced embryologists. Neonatal sex was confirmed through live birth documentation. Morphokinetic parameters and day 3 and day 5 KID scores of male and female embryos were compared. Maternal baseline and treatment characteristics were similar between groups. Morphokinetic time-lapse parameters of male and female embryos including: pronuclei fading; cleavage timings (t2-t9); second and third cell cycle durations; synchrony of the second and third cleavages; late morphokinetic parameters and KID scores did not differ between groups. In conclusion, time-lapse morphokinetic parameters and embryo selection methods do not seem to differ between male and female embryos, and their utilization does not bias towards any neonatal sex.

Sex ratio of offspring is not statistically altered following pre-implantation genetic testing under a specific sex selection policy

PURPOSE

To determine whether the use of pre-implantation genetic testing (PGT) under a specific sex selection policy is associated with alterations in offspring sex ratio.

METHODS

This was a single-center retrospective cohort study of singleton live births from January 2018-December 2020 achieved via single blastocyst non-PGT or PGT frozen embryo transfer (FET). Per institutional policy, sex may be disclosed following PGT. If both sexes are available and morphologic grade is similar, patients may select the sex of the embryo to be transferred. Demographics and cycle characteristics were compared between non-PGT vs. PGT cycles with Mann-Whitney U or χ2. Poisson regression with robust variance estimates was used to model the probability of female vs. male offspring among non-PGT vs. PGT cycles, reported as risk ratio (RR) and 95% confidence interval (CI).

RESULTS(S)

Among 541 live births, 350 (64.7%) were achieved with PGT and 191 (35.3%) without PGT. In both groups, female sex was more common, representing 59.4% of PGT-offspring and 55.0% of non-PGT offspring. After adjusting for potential confounders, the use of PGT was not significantly associated with an increased likelihood of female offspring (RR 1.04, 95% CI 0.98-1.11, p = 0.22).

CONCLUSION(S)

Singletons born following FET had a higher rate of female sex than male. Allowing sex selection per institutional policy did not increase this ratio. These results contrast with those of prior publications and should motivate individual centers to monitor their own sex ratios. As utilization of PGT increases, local, regional, and national monitoring will become increasingly important.

Factors affecting male-to-female ratio at birth in frozen-thawed embryo transfer cycles: a large retrospective cohort study

Background

ICSI (intracytoplasmic sperm injection) leads to a reduced male-to-female ratio at birth, whereas blastocyst transfer results in an increased male-to-female ratio. However, limited knowledge exists regarding the impact of these factors on the live birth rate for each gender. This study aimed to investigate the influence of patient characteristics and treatment parameters on the live birth rate for each gender, as well as the ultimate male-to-female ratio at birth in frozen-thawed embryo transfer (FET) cycles.

Method

This retrospective cohort study involved a total of 28,376 FET cycles and 9,217 subsequent deliveries, spanning from January 2003 to December 2015. The study consisted of two parts. First, logistic regression models were constructed to determine the factors influencing the male-to-female ratio among babies born after FET. Second, we aimed to investigate the mechanisms underlying this sex ratio imbalance by analyzing data from all transfer cycles. Generalized estimated equations were employed to assess the impact of risk factors on rates of male and female live births separately.

Results

ICSI resulted in a lower proportion of male offspring compared to in vitro fertilization (IVF) (50.1% vs. 53.7%, aOR: 0.87, 95% CI: 0.80-0.96). Conversely, blastocyst transfer yielded a higher proportion of male offspring than cleavage-stage embryo transfer (58.7% vs. 51.6%, aOR: 1.32, 95% CI: 1.17-1.48). Analysis of all cycles indicated that ICSI resulted in a reduced likelihood of male live birth in comparison to IVF (19.8% vs. 21.6%, aOR: 0.90, 95% CI: 0.83-0.97). However, the transfer of blastocysts rather than cleavage-stage embryos not only increased the chance of male live birth (26.9% vs. 20.2%, aOR: 1.70, 95% CI:1.56-1.85) but also facilitated female live birth (20.3% vs. 19.3%, aOR: 1.26, 95% CI: 1.15-1.39).

Conclusion

ICSI was associated with a reduction in the male-to-female sex ratio and a lower rate of male live births, while blastocyst transfer was associated with an increased male-to-female sex ratio at birth and a higher rate of male live births.

Recurrence risk and risk factors for monozygotic twin and triplet birth in over 65,000 single-embryo transfers

PURPOSE

To determine the recurrence risk and risk factors for monozygotic splitting after elective single-embryo transfers (eSET).

METHODS

A retrospective cohort study was performed investigating 65,664 eSET cycles that resulted in a clinical pregnancy as reported in the Society for Assisted Reproductive Technology (SART) Clinical Outcomes Reporting System (CORS) between 2004 and 2017. Monozygosity was defined as more than one fetal heart tone by the first-trimester ultrasound and concordant sex at live birth. The primary outcome was recurrence risk, with recurrence defined as one patient having two or more cycles of eSET resulting in monozygotic multiples. The secondary objective was to identify factors associated with smonozygotic splitting, using a multivariable logistic regression model and a stepwise purposeful model selection.

RESULTS

There were 1355 (2.05%) pregnancies that resulted in two or more fetal heart tones after SET, including 840 monozygotic twins and triplets at birth. Recurrence occurred in two cases-0.0001% of patients with multiple eSET cycles. One case resulted from embryos created from a single cohort with intracytoplasmic sperm injection (ICSI), assisted hatching (AH), and blastocyst transfers. The second case resulted from donor egg embryos with ICSI and blastocyst transfers. Risk factors associated with monozygotic live birth were blastocyst transfer (OR 1.23, 95% CI 1.04-1.47, P = 0.0176) and AH (OR 1.23, 95% CI 1.05-1.44, P = 0.0081).

CONCLUSION

Recurrence of monozygotic live births in eSET was very rare. Blastocyst transfer and AH were confirmed to be risk factors for monozygotic live births, while ICSI, PGT, and FET do not appear to be associated.

Chlormadinone acetate in progestin-primed ovarian stimulation does not negatively affect clinical results

Purpose

To investigate whether progestin-primed ovarian stimulation (PPOS) with chlormadinone acetate (CMA) adversely affects clinical results and neonatal outcomes, or causes congenital deformities.

Methods

This retrospective study was conducted at private IVF clinic from November 2018 to November 2021. Women underwent oocyte retrieval using gonadotropin-releasing hormone (GnRH) antagonist protocol (n = 835) or PPOS protocol (n = 57) were included. Eligible patients were normal ovarian responders (aged <40, AMH ≧1.0 ng/mL) with freeze-all cycle. Embryo developments, clinical results, or neonatal outcomes of singletons derived from transfer of frozen single blastocysts were compared within each group.

Results

Patient characteristics were similar in both groups. The median LH level (mIU/mL) at trigger in the GnRH antagonist group [2.0 (1.2-3.7)] was significantly higher than in the PPOS group [0.9 (0.3-1.7)]. There was no cycle with premature LH surge in the PPOS group. Fertilization and blastocyst formation rates did not differ significantly between groups. Furthermore, clinical outcomes were also similar in the two groups. Congenital abnormality rates did not differ significantly [0.9% (3/329), 0.0% (0/17)].

Conclusions

CMA using ovarian stimulation did not negatively affect clinical results. Our data suggest that PPOS with CMA is an appropriate ovarian stimulation method for normal ovarian responders.

Congenital anomaly and perinatal outcome following blastocyst- vs cleavage-stage embryo transfer: systematic review and network meta-analysis

OBJECTIVES

To compare the reported rate of any congenital anomaly and perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer using a pairwise meta-analysis and to evaluate the same outcomes following fresh-blastocyst, frozen-blastocyst, fresh-cleavage or frozen-cleavage embryo transfer using a network meta-analysis.

METHODS

A literature search was performed in PubMed, Scopus and CENTRAL and registers for ongoing studies, from inception to February 2022, for randomized controlled trials (RCTs) with any sample size and observational studies including at least 100 live births per group, comparing the rates of any congenital anomaly and perinatal outcome of pregnancy following fresh/frozen embryo transfer at cleavage (day 2-3) vs blastocyst (day 5-7) stage. Risk ratios (RRs) along with their 95% CIs were pooled via a random-effects model meta-analysis. Within a frequentist network meta-analysis framework, outcomes of all four treatment modalities (i.e. fresh-blastocyst, fresh-cleavage, frozen-blastocyst, frozen-cleavage) were compared further. Any congenital anomaly constituted the primary outcome, whereas preterm delivery (delivery < 37 weeks), low birth weight (LBW; < 2500 g), gender of the neonate (male), perinatal death and healthy neonate (defined as liveborn neonate, delivered at term, weighing ≥ 2500 g, surviving for at least 28 days postbirth and without any congenital anomaly) were considered as secondary outcomes. Subgroup analyses by plurality (liveborn singleton vs multiple pregnancy) were conducted in the pairwise and network meta-analyses. The risk of bias was assessed using the RoB2 tool for RCTs and the ROBINS-I tool for non-randomized studies. Certainty of evidence was assessed using GRADE.

RESULTS

Through the literature search, 550 studies were retrieved and 33 were included in the systematic review. We found no significant difference in the risk for any congenital anomaly between blastocyst- and cleavage-stage transfer (RR, 0.80 (95% CI, 0.63-1.03); 10 studies; n = 192 442; I²  = 85.5%). An increased probability of a male neonate was observed following blastocyst- vs cleavage-stage transfer (RR, 1.07 (95% CI, 1.06-1.09); 18 studies; n = 227 530; I²  = 32.7%). No significant differences in other secondary outcomes or significant subgroup differences between liveborn singletons and multiple pregnancies were observed. The network meta-analysis showed a significantly lower risk for LBW following frozen-blastocyst vs fresh-blastocyst (RR, 0.76 (95% CI, 0.60-0.95)) or fresh-cleavage (RR, 0.74 (95% CI, 0.59-0.93)) transfer. Frozen-blastocyst transfer was associated with an increased risk for perinatal death compared with the fresh-cleavage method (RR, 2.06 (95% CI, 1.10-3.88)). The higher probability of a male neonate following blastocyst transfer remained evident in the network comparisons. All outcomes were assessed to be of very-low certainty of evidence.

CONCLUSIONS

Current very-low certainty of evidence shows that there may be little-to-no difference in the risk for congenital anomaly or adverse perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer, although there was a slightly increased probability of a male neonate following blastocyst transfer. When considering cryopreservation, frozen-blastocyst transfer was associated with a reduction in the risk for LBW compared with both fresh-transfer modalities, and fresh-cleavage transfer may be associated with a reduction in the risk for perinatal death compared with frozen-blastocyst transfer. High-quality RCTs with separate data on fresh and frozen cycles and consistent reporting of culture conditions and freezing methods are mandatory. Individual participant data meta-analyses are required to address the substantial inconsistency resulting from current aggregate data approaches. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Comparison of frozen-thawed embryo transfer strategies for the treatment of infertility in young women: a retrospective study

Objective

To investigate transfer strategies in the frozen-thawed embryo transfer (FET) cycle.

Methods

The clinical data of 1,652 FET patients were divided into five groups according to the number and quality of the transferred blastocyst: high-quality single blastocyst group (group A, n = 558), high-quality plus poor-quality double blastocyst group (group B, n = 435), poor-quality double blastocyst group (group C, n = 241), high-quality double blastocyst group (group D, n = 298), and poor-quality single blastocyst group (group E, n = 120). Inter-group comparison analyses of primary conditions, pregnancy outcomes and neonatal outcomes were then performed.

Results

Group A had the highest embryo implantation rate (67.38%), significantly different from the implantation rates of the other four groups. The gemellary pregnancy rate (1.60%), preterm birth rate (5.58%), neonatal birth weight (3,350g [3,000g, 3,650g]), neonatal birth age (39.57 weeks [38.71, 40.34]), and incidence of low birth weight (7.02%) in group A were different from those in groups B, C, and D, but did not significantly differ from those in group E. Moreover, the proportions of male infants born in groups A (56.86%) and D (59.41%) were significantly higher than those in the other three groups. Double blastocyst transfer (0.528, 95% CI [0.410-0.680], P < 0.001) and high-quality blastocyst transfer (0.609, 95% CI [0.453-0.820], P = 0.001) were found to be protective factors for live birth. In addition, double blastocyst transfer was also the largest risk factor for pregnancy complications (3.120, 95% CI [2.323-4.190], P < 0.001) and neonatal complications (2.230, 95% CI [1.515-3.280], P < 0.001), especially for gemellary pregnancy (59.933, 95% CI [27.298-131.58], P < 0.001) and preterm birth (3.840, 95% CI [2.272-6.489], P < 0.001). Based on the ROC curves, a double blastocyst transfer could predict gemellary pregnancy reliably with a high area under the curve (AUC = 78.53%). Additionally, a double blastocyst transfer could effectively predict a high risk of pregnancy complications (AUC = 65.90%), neonatal complications (AUC = 64.80%) and preterm birth (AUC = 66.20%).

Conclusion

The live birth rate of frozen-thawed high-quality single blastocyst transfer is lower than that of double high-quality blastocyst transfer, which can significantly increase the embryo implantation rate. High-quality single blastocyst transfer also significantly lowers the risk of gemellary pregnancy, preterm birth, and low birth weight, and can significantly improve maternal and infant outcomes. After weighing the pros and cons of live birth with pregnancy and neonatal complications, the authors believe that high-quality single blastocyst transfer is the optimal FET strategy for young women and is worthy of further clinical application. Despite this recommendation, high-quality single blastocyst transfer can increase the risk of monozygotic twins, as well as significantly increase the proportion of male infants born.

Updates in Assisted Reproduction

There are multiple reasons for which the “updates in assisted reproduction” topic is and will be in the center of scientific attention—both clinical and laboratory—during the next decades. In this editorial, we present and discuss some of them.

Placental Abnormalities are Associated With Specific Windows of Embryo Culture in a Mouse Model

Assisted Reproductive Technologies (ART) employ gamete/embryo handling and culture in vitro to produce offspring. ART pregnancies have an increased risk of low birth weight, abnormal placentation, pregnancy complications, and imprinting disorders. Embryo culture induces low birth weight, abnormal placental morphology, and lower levels of DNA methylation in placentas in a mouse model of ART. Whether preimplantation embryos at specific stages of development are more susceptible to these perturbations remains unresolved. Accordingly, we performed embryo culture for several discrete periods of preimplantation development and following embryo transfer, assessed fetal and placental outcomes at term. We observed a reduction in fetal:placental ratio associated with two distinct windows of preimplantation embryo development, one prior to the morula stage and the other from the morula to blastocyst stage, whereas placental morphological abnormalities and reduced imprinting control region methylation were only associated with culture prior to the morula stage. Extended culture to the blastocyst stage also induces additional placental DNA methylation changes compared to embryos transferred at the morula stage, and female concepti exhibited a higher loss of DNA methylation than males. By identifying specific developmental windows of susceptibility, this study provides a framework to optimize further culture conditions to minimize risks associated with ART pregnancies.

Blastocyst morphology is associated with the incidence of monozygotic twinning in assisted reproductive technology

BACKGROUND

An increased incidence of monozygotic twinning after a blastocyst transfer has been previously reported in assisted reproductive technology treatment. It is uncertain whether this phenomenon is due to the extended culture time, culture medium, or inherent blastocyst parameters.

OBJECTIVE

This study aimed to investigate the association between blastocyst parameters (in vitro culture time, blastocyst stage, and inner cell mass and trophectoderm grading) and the incidence of monozygotic twinning after assisted reproductive technology.

STUDY DESIGN

This was a retrospective cohort study employing data from a multicenter, large, electronic database from 4 academic hospitals. All clinical pregnancies after a single blastocyst transfer between January 2014 and February 2020 were included. Blastocyst morphology was evaluated based on the Gardner grading system, considering the blastocyst stage, and inner cell mass and trophectoderm grading (grades A, B, and C). Monozygotic twinning was defined as ≥2 fetal heartbeats in a single gestational sac or 2 gestational sacs with sex concordance at birth. The multivariable predicted marginal proportions from logistic regression models were used to compute adjusted relative risks for the association between blastocyst parameters and the incidence of monozygotic twinning.

RESULTS

The overall monozygotic twinning rate was 1.53% (402 of 26,254 cases). The monozygotic twinning was not associated with the culture time in vitro (day 5 vs day 6) or blastocyst stage (early, blastocyst, expanded, hatching, and hatched). Alternatively, monozygotic twinning was associated with lower inner cell mass grading (B vs A: adjusted relative risk, 1.67 [95 % confidence interval, 1.28-2.25]; C vs A: adjusted relative risk, 1.98 [95% confidence interval, 1.18-3.11]) and higher trophectoderm grading (B vs C: adjusted relative risk, 1.38 [95% confidence interval, 1.03-1.92]; A vs C: adjusted relative risk, 2.14 [95% confidence interval, 1.45-3.20]). The incidence of monozygotic twinning was the lowest in blastocysts with grade A inner cell mass and grade B or C trophectoderm (0.82%, as the reference) and the highest in blastocysts with grade B or C inner cell mass and grade A trophectoderm (2.40%; adjusted relative risk, 2.62; 95% confidence interval, 1.60-4.43). The incidence of monozygotic twinning in blastocysts with consistent inner cell mass or trophectoderm grading was somewhere in between (both A: 1.58%; adjusted relative risk, 1.86 [95% confidence interval, 1.23-3.04]; both B or C: 1.59%; adjusted relative risk, 1.84 [95% confidence interval, 1.29-2.90]).

CONCLUSION

Higher risk of monozygotic twinning was associated with blastocyst morphology specific to those blastocysts with loosely arranged inner cell mass cells combined with tightly packed trophectoderm cells.

The Risk of Congenital Anomalies by Fertility Treatment Modality

Importance

Up to 4% of all births in developed nations involve assisted reproductive technology (ART), along with other fertility treatment modalities. Thus, ART pregnancies constitute an important epidemiologic population with a known increased risk of congenital anomalies. In this review, we summarize current fertility treatment modalities and their associated risk of congenital anomalies.

Objective

To review the risk of birth defects among pregnancies conceived with ART and other fertility treatments.

Evidence Acquisition

Articles were obtained from PubMed and the American College of Obstetricians and Gynecologists and American Society of Reproductive Medicine committee opinions.

Results

In vitro fertilization has been associated with a 25% to 50% increased risk of birth defects, including abnormalities of these organ systems: cardiovascular (25%-40% of anomalies), genitourinary (10%-60%), gastrointestinal (10%-20%), and musculoskeletal (10%-35%). Although the data are mixed, intracytoplasmic sperm injection has also been found to be associated with an increased risk of defects, particularly hypospadias, when compared with conventional in vitro fertilization. The risk among fresh versus frozen cycles and cleavage stage versus blastocyst transfers remains uncertain. There appears to be no significant added risk with preimplantation genetic testing, although more studies are needed. Ovulation induction with oral agents appears safe and not associated with an increased risk of anomalies. Oocyte cryopreservation also appears safe, but the data are still limited, requiring future investigation.

Conclusions and Relevance

While the relative risk of birth defects among ART pregnancies is increased when compared with spontaneous conceptions, the absolute risk remains low. There are no standard screening recommendations for ART pregnancies. Per the American College of Obstetricians and Gynecologists, patients who have undergone ART should be counseled regarding the risk of birth defects and available antenatal evaluation, including fetal echocardiogram and detailed ultrasound evaluation.

Embryo quality, ploidy, and transfer outcomes in male versus female blastocysts

PURPOSE

The goal is to determine if variations exist between male and female blastocysts in preimplantation measurements of quality and ploidy and in vitro fertilization elective single-embryo transfer (eSET) outcomes.

METHODS

A retrospective chart review was conducted from a private fertility center's database of blastocysts undergoing preimplantation genetic testing for aneuploidy, along with details of eSET from this screened cohort. Main outcomes included preimplantation embryo quality and sex-specific eSET outcomes.

RESULTS

A total of 3708 embryos from 578 women were evaluated, with 45.9% male and 54.1% female. The majority were High grade. No difference existed between embryo sex and overall morphological grade, inner cell mass or trophectoderm grade, or blastocyst transformation day. Female blastocysts had a higher aneuploidy rate than male blastocysts (P < 0.001). Five hundred thirty-nine eSETs from 392 women were evaluated, with High grade embryos more likely to have implantation (P < 0.001), clinical pregnancy (P < 0.001), and ongoing pregnancy (P = 0.018) than Mid or Low grade embryos. Day 5 blastocysts were more likely to have implantation (P = 0.018), clinical pregnancy (P = 0.005), and ongoing pregnancy (P = 0.018) than day 6 blastocysts. Male and female embryos had similar transfer outcomes, although female day 5 blastocysts were more likely to result in clinical pregnancy (P = 0.012), but not ongoing pregnancy, than female day 6 blastocysts. Male eSET outcomes did not differ by blastocyst transformation day.

CONCLUSION

Male and female embryos have comparable grade and quality; however, female embryos were more likely to be aneuploid. Ongoing pregnancy rates did not differ by embryo sex. Day 5 embryos had more favorable transfer outcomes than day 6 embryos.

Cumulative live birth rates following blastocyst- versus cleavage-stage embryo transfer in the first complete cycle of IVF: a population-based retrospective cohort study

STUDY QUESTION

Is there a difference in the odds of a live birth following blastocyst- versus cleavage-stage embryo transfer in the first complete cycle of IVF?

SUMMARY ANSWER

After adjusting for indication bias, there was not enough evidence to suggest a difference in the odds of live birth following blastocyst- versus cleavage-stage embryo transfer in the first complete cycle of IVF.

WHAT IS KNOWN ALREADY

Replacement of blastocyst-stage embryos has become the dominant practice in IVF but there is uncertainty about whether this technique offers an improved chance of cumulative live birth over all fresh and frozen-thawed embryo transfer attempts associated with a single oocyte retrieval.

STUDY DESIGN, SIZE, DURATION

National population-based retrospective cohort study of 100 610 couples who began their first IVF/ICSI treatment at a licenced UK clinic between 1 January 1999 and 30 July 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data from the Human Fertilisation and Embryology Authority (HFEA) register on IVF/ICSI treatments using autologous gametes between 1999 and 2010 were analysed. The primary outcome was the live birth rate over the first complete cycle of IVF. Cumulative live birth rates (CLBR) were compared for couples who underwent blastocyst and cleavage transfer, and the adjusted odds of live birth over the first complete cycle were estimated for each group using binary logistic regression. This analysis was repeated within groups of female age, oocytes collected and primary versus secondary infertility. Inverse probability of treatment weighting was used to account for the imbalance in couple characteristics between treatment groups.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 94 294 (93.7%) couples had a cleavage-stage embryo transfer while 6316 (6.3%) received blastocysts. Over the first complete cycle of IVF/ICSI (incorporating all fresh and frozen-thawed embryo transfers associated with the first oocyte retrieval), the CLBR was increased in those who underwent blastocyst transfer (56.5%) compared to cleavage-stage embryo transfer (34.8%). However, after accounting for the imbalance between exposures, blastocyst transfer did not significantly influence the odds of live birth over the first complete cycle (adjusted odds ratio: 1.03 (0.96, 1.10)).

LIMITATIONS, REASONS FOR CAUTION

Limitations of our study include the retrospective nature of the HFEA dataset and availability of linked data up until 2010. We were unable to adjust for some confounders, such as smoking status, BMI and embryo quality, as these data are not collected at national level by the HFEA. Similarly, there may be unknown couple, treatment or clinic variables that may influence our results. We were unable to assess the intended stage of embryo transfer for women who did not have an embryo replaced, and therefore excluded them from our study. Perinatal outcomes were not included in our analyses and would be a useful basis for future study.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings show that blastocyst-stage embryo transfer may offer an improved chance of live birth in both the first fresh and the first complete cycle of IVF/ICSI compared to cleavage-stage transfer, even in couples with typically poorer prognoses. Where possible, offering blastocyst transfer to a wider range of couples may increase cumulative success rates.

STUDY FUNDING/COMPETING INTEREST(S)

N.J.C. received a Wolfson Foundation Intercalated Degree Research Fellowship funded by the Wolfson Foundation, through the Royal College of Physicians. This work was supported by a Chief Scientist Office Postdoctoral Training Fellowship in Health Services Research and Health of the Public Research (Ref PDF/12/06) held by D.J.M. The views expressed here are those of the authors and not necessarily those of the Chief Scientist Office or the Wolfson Foundation. The funders did not have any role in the study design; in the collection, analysis and interpretation of data; in the writing of the report; nor in the decision to submit the paper for publication. None of the authors has any conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Obstetric and perinatal risks in 4601 singletons and 884 twins conceived after fresh blastocyst transfers: a Nordic study from the CoNARTaS group

STUDY QUESTION

Are obstetric and perinatal outcomes in pregnancies after fresh blastocyst transfer (BT) comparable with those born after fresh cleavage stage transfer (CT) and spontaneous conception (SC)?

SUMMARY ANSWER

Fresh BT is associated with a higher risk of placental and perinatal complications.

WHAT IS KNOWN ALREADY

BT optimizes the selection of top-quality embryos and increases pregnancy and live birth rates per transfer compared to CT. However, concerns have been raised as extended culture duration may increase obstetric complications and impair perinatal outcomes. Previous studies have shown a higher risk of preterm birth (PTB) among infants born after BT compared with CT. Pregnancies after BT are also prone to a higher risk of same-sex twins after single embryo transfer (SET).

STUDY DESIGN, SIZE, DURATION

A retrospective register-based cohort study used data from Denmark, Norway and Sweden including three cohorts: 56 557 singletons and 16 315 twins born after fresh IVF/ICSI cycles and 2 808 323 SC singletons in Denmark (birth years 1997-2014), Norway (2010-2015) and Sweden (2002-2015). Of the fresh IVF/ICSI singletons, 4601 were born after BT and 51 956 after CT. The twin cohort consisted of 884 fresh IVF/ICSI children born after BT and 15 431 fresh IVF/ICSI children born after CT.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were obtained from a large Nordic cohort of children born after ART and SC initiated by the Committee of Nordic ART and Safety (CoNARTaS). The CoNARTaS cohort was established by cross-linking National ART-, Medical Birth-, and National Patients Registers using the unique personal identification number, allocated to every citizen in the Nordic countries. Obstetric and perinatal outcomes after BT, CT and SC were compared using logistic regression analysis. For perinatal outcomes, we calculated gestational age based on the date of oocyte pick-up (OPU) and in sensitivity analyses on data from Denmark and Norway, we also calculated gestational age based on the second-trimester ultrasonography (US) scan. Risk of pregnancies with same-sex twins after SET was used as a proxy for risk of monozygotic twins. Adjustments were made for child's sex, birth year, parity (0 or >1), maternal age, body mass index, smoking, educational level, fertilization method (IVF/ICSI), the number of aspirated oocytes, SET and country. Information on educational level and the number of aspirated oocytes was not available for Norway. Children born after frozen embryo transfer were not included. The birth cohorts were restricted according to the year in which BT was introduced in the different countries.

MAIN RESULTS AND THE ROLE OF CHANCE

A higher risk of placenta previa was found in singleton pregnancies after BT compared with CT (adjusted odds ratio [aOR] 2.11 [95% CI 1.76; 2.52]). Singletons born after BT had a higher risk of PTB (aOR 1.14 [95% CI 1.01; 1.29]) compared with CT singletons, when estimated based on OPU. Furthermore, an altered male/female ratio (aOR 1.13 [95% CI 1.06; 1.21]) with more males following BT compared with CT was seen. Risk of same-sex twins after SET was higher after single BT compared with single CT (aOR 1.94 [95% CI 1.42; 2.60]).

LIMITATIONS, REASONS FOR CAUTION

Residual confounding cannot be excluded, in particular related to duration and cause of infertility that we could not adjust for due to lack of reliable data.

WIDER IMPLICATIONS OF THE FINDINGS

Extended embryo culture to the blastocyst stage has the potential to compromise obstetric and perinatal outcomes in fresh cycles. These results are important since an increasing number of IVF/ICSI treatments are performed as BT.

STUDY FUNDING/COMPETING INTEREST(S)

NORDFORSK (project no: 71450). The Research Fund of Rigshospitalet, Copenhagen University Hospital. ReproUnion Collaborative study, co-financed by the European Union, Interreg V ÖKS. Grants from Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (LUA/ALF 70940), Hjalmar Svensson Research Foundation. The Research Council of Norway through its Centres of Excellence funding scheme, project number 262700. None of the authors has any conflicts of interests to declare regarding this study.

TRIAL REGISTRATION NUMBER

ISRCTN11780826.

The mystery of monozygotic twinning II: What can monozygotic twinning tell us about Amyoplasia from a review of the various mechanisms and types of monozygotic twinning?

Monozygotic (MZ) twins ("identical twins") are essentially unique to human beings. Why and how they arise is not known. This article reviews the possible different types of MZ twinning recognized in the previous article on twins and arthrogryposis. There appear to be at least three subgroups of MZ twinning: spontaneous, familial, and those related to artificial reproductive technologies. Each is likely to have different etiologies and different secondary findings. Spontaneous MZ twinning may relate to "overripe ova." Amyoplasia, a specific nongenetic form of arthrogryposis, appears to occur in spontaneous MZ twinning and may be related to twin-twin transfusion.

Incidence and risk factors for velamentous umbilical cord insertion in singleton pregnancies after assisted reproductive technology

AIM

Assisted reproductive technology (ART) is gaining popularity worldwide. However, it is associated with increased incidence of velamentous umbilical cord insertion (VCI) in the placenta, resulting in adverse perinatal outcomes. This study aimed to identify the risk factors that might affect the incidence of VCI in pregnancies after ART treatment.

METHODS

We retrospectively analyzed the records of 906 singleton pregnancies via ART; all women delivered in our facility. Three ART-related variables and infant sex were examined: (1) fertilization method (conventional in vitro fertilization or intracytoplasmic sperm injection), (2) type of embryo at the time of transfer (fresh or frozen-thawed), (3) developmental stage of embryo at the time of transfer (cleavage stage or blastocyst), and (4) infant sex (male or female). Logistic regression analysis was used to assess the impact of these variables on the incidence of VCI.

RESULTS

Of 906 cases, 55 had VCI (incidence rate, 6.1%). After adjusting for potential confounders, blastocyst stage of development (adjusted odds ratio [aOR]: 4.3, 95% confidence interval [CI]: 1.9-12.7) and female sex (aOR: 2.2, 95% CI: 1.2-3.9) emerged as independent risk factors for the development of VCI. The fertilization method and type of embryo at the time of transfer did not affect the incidence of VCI.

CONCLUSIONS

Blastocyst stage of development and female sex pose a higher risk for developing VCI. Thus, more attention should be paid to pregnancies achieved by blastocyst and with a female fetus to detect VCI proactively and safeguard the health of both mother and fetus/neonate.

Increased male live-birth rates after blastocyst-stage frozen-thawed embryo transfers compared with cleavage-stage frozen-thawed embryo transfers: a SART registry study

Objective

To investigate whether there is a difference in live-birth gender rates in blastocyst-stage frozen-thawed embryo transfers (FETs) compared with those in cleavage-stage FETs.

Design

Retrospective cohort study.

Setting

Academic medical center.

Patient(s)

All women with recorded live births who underwent FET at either the blastocyst or cleavage stage, reported to the Society for Assisted Reproductive Technology during 2004–2013.

Intervention(s)

None.

Main Outcome Measure(s)

The primary outcome was live-birth gender rates. Demographic criteria were also collected. The chi-square analyses were used for bivariate associations, and multiple logistic regression models were used for adjusted associations, with all two-sided P<.05 considered statistically significant.

Result(s)

A statistically significant increase was noted in the number of live male births after blastocyst-stage FET compared with that after cleavage-stage FET (51.9% vs. 50.5%). After controlling for potential confounders including age (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.03, 1.08), body mass index (OR, 1.08; 95% CI, 1.04, 1.12), and male factor infertility (OR, 1.06; 95% CI, 1.03, 1.08), the increase in male live births after blastocyst-stage FET remained statistically significant.

Conclusion(s)

In patients undergoing FETs, blastocyst-stage transfers are associated with higher male gender live-birth rates compared with cleavage-stage transfers.

Comparing the cumulative live birth rate of cleavage-stage versus blastocyst-stage embryo transfers between IVF cycles: a study protocol for a multicentre randomised controlled superiority trial (the ToF trial)

INTRODUCTION

In vitro fertilisation (IVF) has evolved as an intervention of choice to help couples with infertility to conceive. In the last decade, a strategy change in the day of embryo transfer has been developed. Many IVF centres choose nowadays to transfer at later stages of embryo development, for example, transferring embryos at blastocyst stage instead of cleavage stage. However, it still is not known which embryo transfer policy in IVF is more efficient in terms of cumulative live birth rate (cLBR), following a fresh and the subsequent frozen-thawed transfers after one oocyte retrieval. Furthermore, studies reporting on obstetric and neonatal outcomes from both transfer policies are limited.

METHODS AND ANALYSIS

We have set up a multicentre randomised superiority trial in the Netherlands, named the Three or Fivetrial. We plan to include 1200 women with an indication for IVF with at least four embryos available on day 2 after the oocyte retrieval. Women are randomly allocated to either (1) control group: embryo transfer on day 3 and cryopreservation of supernumerary good-quality embryos on day 3 or 4, or (2) intervention group: embryo transfer on day 5 and cryopreservation of supernumerary good-quality embryos on day 5 or 6. The primary outcome is the cLBR per oocyte retrieval. Secondary outcomes include LBR following fresh transfer, multiple pregnancy rate and time until pregnancy leading a live birth. We will also assess the obstetric and neonatal outcomes, costs and patients' treatment burden.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Central Committee on Research involving Human Subjects in the Netherlands in June 2018 (CCMO NL 64060.000.18). The results of this trial will be submitted for publication in international peer-reviewed and in open access journals.

TRIAL REGISTRATION NUMBER

Netherlands Trial Register (NL 6857).

An elective single cleavage embryo transfer strategy to minimize twin live birth rate based on a prediction model from double cleavage embryos transfer patients

OBJECTIVE

To minimize twin birth rate by establishing an elective single cleavage embryo transfer strategy based on a twin live birth prediction model from fresh double cleavage embryos transfer (cleavage DET) patients.

METHODS

A total of 2478 patients underwent fresh cleavage DET in Nanjing Tower Hospital were enrolled to establish the twin live birth prediction model by logistic regression analysis and the cutoff value was calculated by ROC curve. Another 300 fresh cleavage DET patients and 550 cleavage single-embryo transfer (SET) patients were selected to testify the sensitivity, specificity and usefulness of this model.

RESULTS

The twin live birth probability (TLBP) = e^X /(e^X + 1), e is a natural logarithm, X = -1.763 - (0.319 × female age) + (0.329 × endometrial thickness) + (0.282 × the number of transferred top embryos) - (0.314 × previous transfer times), and the cutoff value of TLBP was 24.2%. The sensitivity of this model for predicting twin live birth was 75.6%, while the specificity was 52.5% in the external validation of 300 DET patients. Furthermore, the validation of 550 SET patients showed that the live birth rate of TLBP value positive patients was significantly higher than that in negative patients (54.3% vs. 35.5%, p < .001). When adopted an elective single cleavage embryo transfer strategy, the patients with a positive TLBP value choose SET, while still undergo DET who with a negative TLBP value, the live birth rate would maintain as 56.7%; however, the twin birth rate would significantly decline to 7.4%.

CONCLUSION

Female age, endometrial thickness, the number of transferred top embryos and previous embryo transfer times were critical variables for the twin live birth prediction model. An elective single cleavage embryo transfer strategy according to this model can maintain the relatively high live birth rate, meanwhile get the acceptable low twin birth rate.

Double trouble? Clinic-specific risk factors for monozygotic twinning

OBJECTIVE

To investigate clinic-specific risk factors for monozygotic twinning (MZT) using a large, electronic database.

DESIGN

Retrospective case-control study.

SETTING

Infertility clinics.

PATIENT(S)

Using an electronic medical record system, viable clinical pregnancy (confirmation of a gestational sac(s) and presence of at least one fetal pole with a heartbeat on first trimester ultrasound), data were obtained from homologous in vitro fertilization (IVF) cycles after single ET from June 1, 2004, to December 31, 2016. Monozygotic twinning was defined as a pregnancy with two fetal heartbeats on ultrasound with sex concordance at birth.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Risk factors for MZT including cycle type, method of insemination, and method of cryopreservation.

RESULT(S)

Of the 28,265 IVF cycles that met inclusion criteria over the study period, 8,749 (31.0%) resulted in a viable intrauterine clinical pregnancy. There were 102 (2.7%) MZT in the fresh cycle cohort and 133 (2.7%) in the frozen cycle cohort. Neither cryopreservation nor the method of cryopreservation was a significant risk factor for MZT. However, the use of sequential media was an independent risk factor for MZT in fresh, but not frozen, ETs (odds ratio = 1.72, 95% confidence interval, 1.10-2.68). Significant differences were seen in the incidence of MZT between clinics, and this difference persisted after controlling for known risk factors (clinic 0, reference; clinic 2, odds ratio = 2.22; 95% confidence interval, 1.48-3.32; clinic 3, odds ratio = 1.93; 95% confidence interval, 1.30-2.87).

CONCLUSION(S)

Differences in MZT rates exist between individual IVF clinics, suggesting that variations in practice patterns may contribute to this event. The present study noted the use of sequential media was an independent risk factor for fresh but not frozen cycles.

Initial serum HCG levels are higher in pregnant women with a male fetus after fresh or frozen single blastocyst transfer: A retrospective cohort study

OBJECTIVE

Substantial previous studies have almost reached an agreement on the gender effect on maternal serum human chorionic gonadotropin (MsHCG) in and after the late first trimester of pregnancy. However, there is little knowledge of the sex-related difference in MsHCG level at the preliminary stage of pregnancy. The purpose of this study is to reveal this difference in women after fresh or frozen single blastocyst transfer (SBT).

MATERIALS AND METHODS

A total of 252 fresh SBT cycles and 1486 frozen-thawed SBT cycles collected between June 1, 2014 and May 30, 2017 were retrospectively analyzed in our center. Patients with MsHCG level ≥5 IU/L on day 11 after transfer, achieving a singleton intrauterine pregnancy and subsequent live birth were included. We compared MsHCG levels between women gave birth to a male neonate and those gave birth to a female one in fresh or frozen SBT cycles, respectively.

RESULTS

A total of 136 neonates including 57 females and 79 males were born following fresh SBT. The male-female ratio was 1.39:1. The average MsHCG level of male fetuses was higher than that of female fetuses on day 11 after transfer (549.82 ± 253.24 IU/L versus 439.03 ± 198.41 IU/L, P < 0.05). Correspondingly, a total of 431 infants was born after frozen SBT, containing 188 females and 243 males. The male-female ratio was 1.29:1. Initial MsHCG level remained higher in women with a male neonate than the counterparts with a female neonate (894.43 ± 622.17 IU/L versus 758.05 ± 624.33 IU/L, P < 0.05). It was also found the pregnant women following frozen-thawed SBT exhibited higher initial MsHCG level than those following fresh SBT in whether male-bearing or female-bearing gestations.

CONCLUSIONS

MsHCG levels are higher in pregnant women with a male fetus than those with a female one on day 11 after fresh or frozen SBT. A sex-specific response to the stress in the process of in vitro embryo culture was suggested.

Perinatal outcome in children born after assisted reproductive technologies

Over the past 40 years access and effectiveness of assisted reproductive technologies (ART) have increased, and to date more than 8 million children have been conceived after ART globally. Most pregnancies resulting from ART are uncomplicated and result in the birth of healthy children. Yet, it is well known that pregnancies following ART are more likely to be affected by obstetric complications such as hypertensive disorders in pregnancy, preterm birth, and low birth weight compared with spontaneously conceived pregnancies. ART children are also at increased risk of birth defects. The majority of the problems arise as a result of multiple pregnancies and can be reduced by transferring a single embryo, thereby avoiding multiple pregnancies. New ART technologies are constantly introduced, and monitoring of the health of ART children is crucial.

Pre-implantation genetic testing alters the sex ratio: an analysis of 91,805 embryo transfer cycles

PURPOSE

To determine if pre-implantation genetic testing (PGT) shifts the sex ratio (SER), the ratio of male to female births in a population normalized to 100 and typically stable at 105, following in vitro fertilization (IVF).

METHODS

Data from 2014 to 2016 was requested from the Society for Assisted Reproductive Technologies (SART) database including fresh and frozen transfer cycles. Women with a singleton live birth following a fresh or frozen autologous embryo transfer of a PGT blastocyst, non-PGT blastocyst, or non-PGT cleavage stage embryo were included. The SER between groups was compared using chi-square tests. Modified Poisson regression modeled the relative risk (RR) of having a male compared to a female among PGT blastocyst transfers versus non-PGT cleavage and blastocyst transfers adjusting for age, BMI, smoking status, race, parity, number of oocytes retrieved, and clinic region.

RESULTS

The SER was 110 among PGT blastocyst offspring, 107 among non-PGT blastocyst offspring (p = 0.005), and 99 among non-PGT cleavage offspring (p < 0.001). The risk of having a male infant was 2% higher among PGT blastocyst transfers compared to non-PGT blastocyst transfers (RR 1.02; 95% CI: 1.01, 1.04). The risk was 5% higher among PGT blastocyst transfers compared to non-PGT cleavage transfers (RR 1.05; 95% CI: 1.02, 1.07). The association between PGT and infant gender did not significantly differ by region (p = 0.57) or parity (p = 0.59).

CONCLUSION

Utilizing PGT shifts the SER in the IVF population from the standard of 105 to 110, increasing the probability of a male offspring.

X chromosome inactivation in human development

X chromosome inactivation (XCI) is a key developmental process taking place in female mammals to compensate for the imbalance in the dosage of X-chromosomal genes between sexes. It is a formidable example of concerted gene regulation and a paradigm for epigenetic processes. Although XCI has been substantially deciphered in the mouse model, how this process is initiated in humans has long remained unexplored. However, recent advances in the experimental capacity to access human embryonic-derived material and in the laws governing ethical considerations of human embryonic research have allowed us to enlighten this black box. Here, we will summarize the current knowledge of human XCI, mainly based on the analyses of embryos derived from in vitro fertilization and of pluripotent stem cells, and highlight any unanswered questions.

Zygotic splitting following embryo biopsy: a cohort study of 207 697 single-embryo transfers following IVF treatment

OBJECTIVE

To evaluate the risk of monozygotic splitting with embryo biopsy during in vitro fertilisation (IVF).

DESIGN

A cohort study.

SETTING

Anonymised assisted reproductive technology national data from the Human Fertilisation and Embryology Authority, UK.

POPULATION

Women undergoing single-embryo transfer (SET) following either pre-implantation genetic testing (PGT) involving embryo biopsy or IVF without PGT.

METHODS

Data on women undergoing SET either following PGT and non-PGT IVF treatment in 2000-2016 were analysed to compare the risk of zygotic splitting and monozygotic twining. Logistic regression analysis was performed adjusting for potential confounders.

MAIN OUTCOMES

Monozygotic spitting, monozygotic twin birth.

RESULTS

Data comprising a total of 207 697 SET cycles (4544 following PGT and 203 153 following non-PGT IVF) were analysed. The live birth rate per embryo transfer was 31.9% (95% confidence interval [CI] 30.5-33.2%) following PGT and 26.9% (95% CI 26.7-27.1%) following non-PGT IVF. The incidence of zygotic splitting following PGT was 2.4% (95% CI 1.7-3.3%) versus 1.5% (95% CI 1.4-1.6%) following non-PGT IVF. There was a significantly higher risk of zygotic splitting with PGT versus non-PGT IVF cycles (odds ratio [OR] 1.64, 95% CI 1.19-2.27). The higher risk of zygotic splitting with PGT cycles remained significant after adjusting for potential confounders (adjusted OR 1.51, 95% CI 1.06-2.15).

CONCLUSIONS

The present study demonstrated an increased risk of monozygotic splitting with embryo biopsy. Given the current sparse literature, it is important to accumulate further evidence to validate the findings.

TWEETABLE ABSTRACT

A likely increased risk of monozygotic splitting following embryo biopsy.

Comparison of the pregnancy and obstetric outcomes between single cleavage-stage embryo transfer and single blastocyst transfer by time-lapse selection of embryos

To compare the pregnancy and obstetric outcomes following single cleavage-stage embryo transfer (SCT) and single blastocyst transfer (SBT) using time-lapse imaging (TLI), a total of 2066 normally fertilized and cleaved embryos from 233 patients were divided into Day 3 SCT group (n = 171) and Day 5 SBT group (n = 62) according to patient's willingness. Embryo selection criteria were based on embryo cleavage patterns, timing parameters, and blastocyst quality. The pregnancy and obstetric outcomes of each group were evaluated. There were no statistically significant differences with regard to pregnancy outcomes including the implantation rate, early abortion rate, ongoing pregnancy rate and live birth rate, and obstetric outcomes including preterm birth rate, gestational week, birth height, birth weight and fetal malformation rate between SCT group and SBT group. SBT group had significantly higher monozygotic twinning (MZT) rates than SCT group (6.98% vs. 0, p < .05). Although not statistically significant, there was a trend of higher proportion of male-to-female sex ratio at birth in SBT group than SCT group (1.38 vs. 1.05). Based on the combination of cleavage patterns and timing parameters, SCT may be an alternative to SBT because it can provide similar pregnancy and obstetric outcomes and meanwhile lower monozygotic twinning rates.

Impact of assisted reproduction, infertility, sex and paternal factors on the placental DNA methylome

Children conceived using Assisted Reproductive Technologies (ART) have a higher incidence of growth and birth defects, attributable in part to epigenetic perturbations. Both ART and germline defects associated with parental infertility could interfere with epigenetic reprogramming events in germ cells or early embryos. Mouse models indicate that the placenta is more susceptible to the induction of epigenetic abnormalities than the embryo, and thus the placental methylome may provide a sensitive indicator of 'at risk' conceptuses. Our goal was to use genome-wide profiling to examine the extent of epigenetic abnormalities in matched placentas from an ART/infertility group and control singleton pregnancies (n = 44/group) from a human prospective longitudinal birth cohort, the Design, Develop, Discover (3D) Study. Principal component analysis revealed a group of ART outliers. The ART outlier group was enriched for females and a subset of placentas showing loss of methylation of several imprinted genes including GNAS, SGCE, KCNQT1OT1 and BLCAP/NNAT. Within the ART group, placentas from pregnancies conceived with in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) showed distinct epigenetic profiles as compared to those conceived with less invasive procedures (ovulation induction, intrauterine insemination). Male factor infertility and paternal age further differentiated the IVF/ICSI group, suggesting an interaction of infertility and techniques in perturbing the placental epigenome. Together, the results suggest that the human placenta is sensitive to the induction of epigenetic defects by ART and/or infertility, and we stress the importance of considering both sex and paternal factors and that some but not all ART conceptuses will be susceptible.

Risk factors for monozygotic twinning after in vitro fertilization: a systematic review and meta-analysis

OBJECTIVES

To establish the risk factors for monozygotic twin (MZT) and monochorionic twin (MCT) pregnancies after in vitro fertilization (IVF).

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Women who achieved MZT and non-MZT pregnancies through IVF.

INTERVENTION(S)

Systematic search of Medline from January 1995 to October 2018 with cross-checking of references from relevant articles in English.

MAIN OUTCOME MEASURE(S)

Possible risk factors for MZT or MCT pregnancies after IVF, comprising extended embryo culture, insemination method (conventional IVF and intracytoplasmic sperm injection [ICSI]), embryo biopsy for preimplantation genetic testing for aneuploidies or for monogenic/single-gene defects (PGT-A or PGT-M) programs, assisted hatching (AH), oocytes donation, female age, and embryo cryopreservation.

RESULT(S)

A total of 40 studies were included. Blastocyst transfer compared with cleavage-stage embryo transfer, and female age <35 years were associated with a statistically significant increase in the MZT and MCT pregnancy rate after IVF: (23 studies, OR 2.16, 95% CI, 1.74-2.68, I²=78%; 4 studies, OR 1.29; 95% CI, 1.03-1.62, I²=62%; and 3 studies, OR 1.90, 95% CI, 1.21-2.98, I²=59%; 2 studies, OR 2.34; 95% CI, 1.69-3.23, I²=0, respectively). Conventional IVF compared with ICSI and assisted hatching were associated with a statistically significantly increased risk of MZT pregnancy (9 studies, OR 1.19, 95% CI, 1.04-1.35, I²=0; 16 studies, OR 1.17, 95% CI, 1.09-1.27, I²=29%, respectively). Embryo biopsy for PGT-A or PGT-M, embryo cryopreservation, and oocytes donation were not associated with MZT pregnancies after IVF.

CONCLUSION(S)

Blastocyst transfer is associated with an increased risk of both MZT and MCT pregnancies after IVF. Further evidence is needed to clarify the impact of female age, insemination method and AH on the investigated outcomes.

Trends and correlates of the sex distribution among U.S. assisted reproductive technology births

OBJECTIVE

To assess national trends in the sex distribution of live-born infants in the assisted reproductive technology (ART) and general population and to identify factors correlated with offspring sex.

DESIGN

Retrospective cohort study.

SETTING

Fertility treatment centers.

PATIENTS

All live-born infants included in the National Vital Statistics System and resulting from ART cycles reported to the National ART Surveillance System during 2006-14.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE(S)

Trends in the proportion of male infants in the general population and proportion of males from fresh ART cycles among all ART live-born infants and singletons after single ET.

RESULT(S)

There were 214,274 live-born infants resulting from fresh ART cycles; 53.5% (5,492/10,266) of infants resulting from PGD/PGS cycles were male, as compared with 50.6% (103,228/204,008) in the non-PGD/PGS group. Among non-PGD/PGS cycles, blastocyst transfer was positively associated with male infants (adjusted risk ratio [aRR] = 1.03; 95% confidence interval [CI], 1.02-1.04). Intracytoplasmic sperm injection was negatively associated with male infants (aRR = 0.94; 95% CI, 0.93-0.95) and for singletons after single ET (aRR = 0.93; 95% CI, 0.90-0.95), as was transfer of two embryos (aRR 0.98; 95% CI, 0.97-0.99) or three or more embryos (aRR = 0.98; 95% CI, 0.96-0.99) among all live births from cycles without PGD/PGS use.

CONCLUSION(S)

The proportion of male live-born infants among ART population did not change during 2006-14, ranging from 50.5% to 51.2%. Factors such as blastocyst transfer, intracytoplasmic sperm injection use, embryo stage, and number of embryos transferred may be associated with infant sex; further investigation is needed to understand possible underlying causes.

Two cases of atypical twinning: Phenotypically discordant monozygotic and conjoined twins

Atypical twinning highlights that complex mechanisms responsible for twinning are not fully understood and may give further insight into the mechanisms involved. To assume that phenotypic difference is the result of dizygotic twinning would be erroneous and could have significant implications in the care and counseling provided to these patients.

Blastocyst culture and transfer in clinically assisted reproduction: a committee opinion

The purposes of this Practice Committee Opinion, which replaces the 2013 ASRM Practice Committee Opinion of the same name (Fertil Steril 2013; 99:667-72), are to review the literature regarding the clinical application of blastocyst transfer and identify the potential risks and laboratory issues related to the use of this technology. This document does not apply to patients undergoing blastocyst culture and transfer for preimplantation genetic testing.

The risk of secondary sex ratio imbalance and increased monozygotic twinning after blastocyst transfer: data from the Japan Environment and Children's Study

BACKGROUND

Some studies have suggested that blastocyst transfer is associated with i) imbalance in the secondary sex ratio (SSR) (which favors male offspring), ii) increased incidence of monozygotic twins (MZT). In contrast, others have not found these changes. In this study, we evaluated the association between blastocyst transfer and SSR and MZT, considering potential parental confounders.

METHODS

The Japan Environment and Children's Study is a large, nationwide longitudinal birth cohort study funded by the Ministry of the Environment of Japan. We used this large dataset, including 103,099 pregnancies, to further investigate the association between blastocyst transfer, SSR and MZT, using spontaneously conceived pregnancies, non-assisted reproductive technology (non-ART) treatment (intrauterine insemination and ovulation induction with timed intercourse) and cleavage stage embryo transfer for comparison. We evaluated the association with each group, the SSR, and the frequency of MZT, calculating the adjusted odds ratio (AOR) using multivariable logistic regression analyses, adjusting for potential parental confounders such as basic health and socioeconomic status.

RESULTS

For each group (spontaneous conception vs. non-ART treatment vs. cleavage stage embryo transfer vs. blastocyst transfer), the percentages of males were 51.3% vs 50.7% vs 48.9% vs 53.4% and the monozygotic twinning rates per pregnancy were 0.27% vs 0.11% vs 0.27% vs 0.99% respectively. Multivariate logistic regression analyses indicated that blastocyst transfer was significantly associated with a higher SSR and higher incidence of MZT than the other three groups (SSR: AOR 1.095, 95% CI1.001-1.198; MZT: AOR 4.229, 95% CI 2.614-6.684).

CONCLUSIONS

There are significant relationships between blastocyst transfer and SSR imbalance and a higher occurrence of MZT.

Determinants of monozygotic twinning in ART: a systematic review and a meta-analysis

BACKGROUND

The incidence of monozygotic twins (MZT) after ART appears to be higher than the incidence after spontaneous conceptions contradicting the aim of ART to avoid multiple pregnancies because of the associated risks.

OBJECTIVE AND RATIONALE

The aim was to study the frequency of MZT after IVF and ICSI and how it is influenced by the day of embryo transfer, maternal age, zona pellucida manipulation, controlled ovarian stimulation, stimulation protocol, culture media and embryo quality.

SEARCH METHODS

Original studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. The inclusion criterion was publications focusing on the five study questions related to MZT in our study. The exclusion criteria were articles that did not include blastocyst transfer, were on non-humans, were not published in peer-reviewed journals, and were based only on case studies. All of the articles were categorized according to the Oxford Centre for Evidence-based Medicine's 'Levels of Evidence', and quality and risk of bias assessment was performed with 'The Cochrane Collaboration's Risk of Bias Tools'. A meta-analysis was performed to study the impact of the day of embryo transfer on the MZT rate.

OUTCOMES

The literature search resulted in a total of 42 articles, including 38 original studies, for analysis. The included original studies reported a MZT rate with blastocyst transfer from zero to 13.2%. Our meta-analysis found a higher frequency of MZT after blastocyst transfer compared with cleavage-stage embryos transfer: odds ratio = 2.18, 95% CI: 1.93-2.48 (fixed effect meta-analysis). A younger maternal age may increase the MZT rate, and recent studies regarding the use of zona pellucida manipulating techniques have disagreed with the previous suspicion of a higher MZT rate after the use of these methods. The extended culture to-blastocyst stage is a potential risk factor for MZT, but it is uncertain whether this phenomenon is due to the extended time, culture media or greater likelihood of younger oocytes to reach the blastocyst stage. An increased frequency of MZT following the GnRH-agonist suppression protocol has been suggested, as well as a decreased frequency of MZT with high gonadotrophin doses, which could reflect an age-related effect. Only limited literature has focused on the role of embryo morphology in the MZT rate, therefore, this issue remains unresolved.

WIDER IMPLICATIONS

We found blastocyst transfer to be a risk factor for MZT. Hence, the results of this meta-analysis may weaken the previously proposed view that greater experience with blastocyst transfer and improved culture media could decrease the high rate of MZT after blastocyst transfer. To minimize the rate of MZT and the associated complications, the mechanisms underlying blastocyst transfer and MZT pregnancy must be elucidated.

Clinical and neonatal outcomes of patients of different ages following transfer of thawed cleavage embryos and blastocysts cultured from thawed cleavage-stage embryos

BACKGROUND

Frozen-thawed embryo transfer (FET) has become a routine procedure in assisted reproductive technology (ART). In FET, although blastocysts cultured from thawed cleavage-stage embryos are associated with better perinatal outcomes. it may increase cycle cancellation due to no suitable embryo to transfer. The overall clinical outcomes following transfer of thawed cleavage-stage FET and blastocysts cultured from thawed cleavage-stage embryos in young and advanced age patients remains unclear. Therefore, we aimed to identify the optimal FET strategy in young and advanced age women who undergo FET.

METHODS

This retrospective study included 16,387 thaw cycles. We retrospectively analyzed data of couples who had completed the first FET cycle. Two FET strategies were studied: transfer of thawed cleavage-stage embryos (strategy A) or blastocysts cultured from thawed cleavage-stage embryos (strategy B). The clinical and neonatal outcomes of two FET strategies were compared in young (<35 years) and advanced (≥35 years) age women.

RESULTS

In young women, the clinical outcomes per transfer cycle were better in strategy B than strategy A. While the clinical pregnancy (59.29%, 52.60%) and live birth rates (49.37%, 43.88%) per thaw cycle were significantly higher in strategy A than in B. In women of advanced age, the clinical outcomes per transfer cycle were still better in strategy B than in A, and the clinical pregnancy (36.44%, 39.66%) and live birth rates (25.70%, 30.00%) per thaw cycle were significantly higher in strategy B than in A.

CONCLUSIONS

FET of blastocysts cultured from cleavage-stage embryos showed higher efficiency for per transfer cycle whether in younger or advanced age women. Whereas, when cycle cancellations due to no suitable embryo to transfer were considered, cleavage-stage FET was found to be more suitable for younger women, while FET of blastocysts cultured from cleavage-stage embryos was better suited for women of advanced age.

The relationship between preimplantation morphokinetics of human embryos and sex chromosome pattern

The aim of this study was to determine the relationship between the gender of human embryos and chronological changes during the two pronuclear (2PN) embryonic stage and blastocyst formation on day five after injection using time-lapse imaging and preimplantation genetic testing. A total of 120 couples who underwent intracytoplasmic sperm injection with preimplantation genetic testing were included in the study. Only normal embryos (n = 416) were enrolled in this study. Time-lapse imaging data of male (n = 227) and female (n = 189) embryo progression was carried out to estimate the times of initial appearance of the 2PN stage, fading times and day five blastulation rates. The results revealed that the 2PN stage (fertilisation) was reached significantly earlier in female embryos (9.09 ± 1.31 h) than in male embryos (9.52 ± 1.48 h, p-value = 0.0044). Conversely, the fading time of 2PN was significantly faster in male embryos (22.13 ± 2.02) than in female embryos (24.16 ± 2.61, p-value < 0.001). The blastulation rate was significantly higher in female than male embryos (68.25% vs. 57.71%; p-value = 0.025).

The use of intracytoplasmic sperm injection is associated with a shift in the secondary sex ratio

RESEARCH QUESTION

What is the association between assisted reproductive technologies and human sex ratio as a proportion of male offspring at birth.

DESIGN

A total of 59,628 singleton deliveries resulting from IVF, intracytoplasmic sperm injection (ICSI) and intrauterine insemination (IUI) or ovulation induction from 101 IVF clinics in Germany, that had been documented in a national German IVF registry, were analysed. Sex ratio after assisted reproductive technology was also compared with the sex ratio reported in the birth records of the German Federal Statistical Office.

RESULTS

The sex ratio was 50.0% (95% CI 49.5% to 50.5%) for ICSI, 52.2% (95% CI 51.5% to 52.9%) for IVF, 52.2% (95% CI 50.9% to 53.5%) for IUI or ovulation induction and 51.3% in the national birth records, respectively. Significant differences existed across the three treatment groups (P = 6.86 × 10^-7) as well as in pairwise comparisons between ICSI versus IVF (P = 6.88 × 10^-7) and ICSI versus IUI or ovulation induction (P = 0.003). No difference existed between the groups IUI or ovulation induction versus IVF. Same results were also present after stratification by maternal age: IVF versus ICSI (P = 6.433 × 10^-7), ICSI versus IUI or ovulation induction (P = 0.003), and IVF versus IUI or ovulation induction (non-significant). Compared with the national birth records, ICSI is associated with a lower sex ratio compared with the reference group (P < 0.001), whereas IVF is associated with a higher sex ratio (P = 0.015).

CONCLUSIONS

The use of ICSI is associated with an equal proportion of sexes at birth, which is not the case for IVF, IUI or ovulation induction, or natural conception. This phenomenon is not influenced by maternal age.

Identifying risk factors related to monozygotic twins after assisted reproductive technologies

OBJECTIVE

This secondary analysis aimed to identify the incidence and risk factors associated with monozygotic twins (MZTs) after assisted reproductive technology (ART).

STUDY DESIGN

In this retrospective cohort observational study, the treatment cycles were compared between MZT and non-MZT pregnancies using logistic regression analyses. Of the 11,501 patients with 13,225 pregnancies, 166 MZTs were diagnosed (1.44% in ART pregnant patients; 1.25% in pregnant cycles).

RESULTS

Results of the logistic analysis revealed that embryo stage at transfer and number of good-quality embryos were independent predictive factors for MZTs. The thresholds for two factors were 3.5 and 3.5. The efficacy of embryo stage at transfer and number of good-quality embryos for MZTs were evaluated using receiver-operating characteristic curves. The areas under the curve (AUCs) for these two parameters were 0.708 and 0.633, respectively. Adding number of good quality embryos increased the discriminative ability of the model (AUC = 0.745).

CONCLUSIONS

The incidence of MZTs, subsequent to ART, is quite high. Extended culture (≥3.5 days), together with the number of good-quality embryos (≥3.5), conferred the greatest risk of producing MZTs.

Neonate female to male ratio after assisted reproduction following antagonist and agonist protocols

We retrospectively compared neonatal sex after antagonist- versus long-stimulation protocols followed by fresh in vitro fertilization (IVF) or fresh intracytoplasmic sperm injection (ICSI) with either protocol. We reviewed data for 762 IVF/ICSI cycles in 2015, including 23 IVF procedures. We summarized sex outcomes in the entire cohort, and for the additional subgroups: embryo transfer day and number of embryos transferred, and number of oocytes recovered and maternal age. Among 169 live births for all protocols combined, 50.9% of babies were male, and we saw no difference between the antagonist versus long-stimulation groups (52.3% vs 48.3% male babies, respectively; P = .740). Our results also showed no significant difference in sex proportion when comparing IVF versus ICSI, although a higher proportion of babies were male with the antagonist-ICSI protocol. Differences between the additional subgroups were also neither clinically nor statistically significant.

Euploidy in relation to blastocyst sex and morphology

PURPOSE

The objective of our study is to assess the relationship of embryo ploidy status in relation to embryo sex, morphological characteristics, and transfer parameters.

METHODS

This is a retrospective cohort study at an academic medical center of patients who underwent in vitro fertilization with preimplantation genetic screening (PGS) from 2010 to 2015. Embryos were screened with 24-chromosome preimplantation genetic screening with day 5/6 trophectoderm biopsy. We investigated embryo euploidy in relation to morphology (expansion, inner cell mass, trophectoderm), embryo sex, biopsy day, and blastocyst cohort size. We used multivariate logistic regression to calculate odds ratios of euploidy in relation to these parameters.

RESULTS

A total of 1559 embryos from 316 cycles and 233 patients (mean maternal age = 37.8 ± 4.2 years) were included in the analysis. Six hundred and twenty-eight blastocysts (40.3%) were found to be euploid. Expansion (p < 0.001), inner cell mass (ICM) (p < 0.01), and trophectoderm grade (p < 0.001) were significantly associated with embryo ploidy in bivariate models controlling for maternal age, while embryo sex, biopsy day, and blastocyst cohort size were not associated with embryo ploidy. In a multivariate model, we found that maternal age (p < 0.001), higher grade of expansion (p < 0.01), and better quality trophectoderm (p < 0.001 for A compared to C grade) remained significantly associated with increased embryo euploidy, but ICM grade was no longer significant. Embryo sex was not associated with ploidy status, though male embryos were found to be associated with higher trophectoderm scores (p < 0.02).

CONCLUSIONS

This is the largest study to date to investigate PGS-tested embryo sex and ploidy status. While maternal age and some morphological parameters (expansion, trophectoderm grade) are associated with euploidy in our cohort, other parameters such as embryo sex, biopsy day, and cohort size are not. Though embryo sex was not associated with euploidy, male embryos were found to be associated with higher trophectoderm grades. Additional investigation in larger studies is warranted.

The effect of blastocyst transfer on newborn sex ratio and monozygotic twinning rate: an updated systematic review and meta-analysis

RESEARCH QUESTION

Is blastocyst transfer (BT) associated with a higher offspring secondary sex ratio and monozygotic twinning (MZT)?

DESIGN

A systematic search of PubMed/MEDLINE, Embase, Web of Science, Cochrane Library and Google Scholar databases was carried out for studies published between 1995 and May 2017 using relevant keywords and a meta-analysis performed on selected studies. The analysis was performed using Stata 12.0; odds ratios (OR) and 95% confidence intervals (CI) were used to assess the results for binary studies. Subgroup analyses and meta-regression were also conducted.

RESULTS

Twenty-six studies published between 2001 and May 2017 (sex ratio: 13, MZT: 12, and both sex ratio and MZT: 1) were identified. The analysis showed a significantly higher M/F ratio at birth (OR = 0.89, 95% CI: 0.86 to 0.93, I² = 19.8%) and a higher risk of MZT (OR = 0.37, 95% CI: 0.22 to 0.60, I² = 75.2%) after BT compared with cleavage-stage embryo transfer (CT). Furthermore, a subgroup analysis was performed based on studies published after 2009; results were found to be consistent with the 2009 meta-analysis.

CONCLUSIONS

This meta-analysis provides an update and stronger evidence to support the observation that BT is associated with a higher proportion of males and an increased risk of MZT. In clinical practice, these BT-associated neonatal outcomes should be taken into account when counselling infertility patients.