Blastocyst transfer and gender: IVF versus ICSI

Some lessons learned from genomic and epigenomic studies of the placenta

Recent attention to the "replicability crisis" in research has led to greater efforts to outline research practices that might improve the quality of research results. Steps to improve replicability through standardisation and control of covariates can be field specific. In this review, we highlight lessons learned through our own and other genome-wide studies of genetic, epigenetic and gene expression variation in the placenta. We share our understanding of the impact of placental genetics, possible confounders, sources of sampling variation, dataset stratification, and adjustment for covariates. Overall, we hope to raise awareness of these study considerations amongst placental researchers.

School-age outcomes among IVF and ICSI-conceived children: a causal inference analysis using linked population-wide data

BACKGROUND

Use of intracytoplasmic sperm injection (ICSI) continues to increase as the most common mode of oocyte insemination during in vitro fertilisation (IVF), sometimes in the absence of clear indications (i.e. male factor infertility). Several studies suggest an increased risk of congenital abnormalities after ICSI. The association between the ICSI technique and long-term childhood development remains unclear.

METHODS

Our population-based study included singleton infants conceived via IVF and born between 2005 and 2013. The cohort included state-wide linked maternal and childhood administrative data from Victoria, Australia. The primary exposure was conception via ICSI (without severe male factor infertility), with those born following standard IVF as controls. Childhood development was examined using the Australian Early Development Census (AEDC), a broad assessment of childhood development across five domains of health and neurodevelopment performed in Australian schools every triennium at school entry (age 4-6 years). Our primary outcome used a validated global measure-developmental vulnerability-defined as scoring less than the 10th percentile in two or more of the five developmental domains (DV2). Causal inference methods were used to analyse observational data in a way that emulates a target randomised clinical trial. The adjustment variable set was determined a priori via a modified Delphi procedure. Given the use of observational data, there were missing data and inherent differences in the covariate profile between exposure cohorts. Multiple imputation, bootstrapping and doubly robust inverse probability weighted regression adjustment modelling was utilised to allow a causal interpretation of results.

RESULTS

Our cohort (N = 3656) included 1489 IVF and 2167 ICSI-conceived children. We found no causal effect of ICSI on the risk of AEDC-defined developmental vulnerability at school-entry age compared with children conceived via standard IVF; adjusted risk difference - 1.11% (95% CI - 4.23 to 2.01%) and adjusted risk ratio 0.90 (95% CI 0.68 to 1.21).

CONCLUSIONS

Our findings suggest that the use of ICSI in IVF cycles without severe male factor infertility does not increase the risk of early childhood developmental vulnerability among children in their first year of school. These findings provide important reassurance for current and prospective parents and clinicians alike.

Diameter of Human Day Five Blastocysts and Birth Sex

Background This study aimed to evaluate the offspring sex ratio, born through fresh and cryo-thawed single blastocyst (BL) transfers regarding a single morphological, static parameter, namely, BL diameter. Methodology This retrospective, observational study was conducted at an assisted reproductive technology (ART) center, Kinderwunschzentrum Niederrhein Germany. We conducted a statistical analysis of all births resulting from fresh and thawed in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles after a single embryo transfer (SET). The main outcome measure was the offspring sex ratio after SET of a day five BL in relation to the BL diameter measurement. Results There were more female than male babies born in our study. We observed a tendency for BL to have a higher diameter, resulting in female offspring, which was not statistically relevant. We also compared the BL diameter in the fresh embryo transfer (ET) group with that of the cryo-thawed ET group, showing a tendency toward a larger diameter in the fresh ET group. In the ICSI cycles, there was a higher tendency for a larger BL diameter when compared to IVF cycles. In the fresh ET cycles, BL leading to the male sex at birth had a tendency toward a larger diameter than the female BL. In the cryo-thaw ET cycles, BL leading to the female sex had a tendency toward a larger diameter than the male BL. Conclusions Our results showed a tendency in the sex of offspring toward the female sex and no significant difference in the BL diameter of BL leading to birth after ART and consecutive transfer of day five BL.

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.

Primary sex ratio in euploid embryos of consanguine couples after IVF/ICSI

PURPOSE

To assess the primary sex ratio (males-to-females at time of conception) in blastocysts from consanguine couples undergoing IVF/ICSI treatments and its correlation with chromosomal constitution.

METHOD

A total of 5135 blastocysts were analyzed by preimplantation-genetic testing for aneuploidy (PGT-A) with next-generation sequencing (NGS) from November 2016 to December 2020. From those, a total of 1138 blastocysts were from consanguine couples (CS) and 3997 from non-consanguine couples (NCS). Only blastocysts presenting normal sex chromosome constitution with or without autosomal aneuploidies were included. Primary sex ratio (PSR) of biopsied blastocysts was compared between CS and NCS couples.

RESULTS

Expanded blastocysts derived from CS had 47.7% XY versus 52.3% XX constitutions, presenting a PSR of 0.91. In NCS, 48.9% of expanded blastocysts were XY and 51.2% XX, with a less pronounced PSR of 0.95. When stratifying embryos by ploidy, euploid embryos from CS had the lowest PSR (0.87) with 46.6% XY versus 53.4% XX blastocysts (OR 0.89, 95% CI 0.70-1.14; NS), but it did not achieve statistical significance. The lower PSR seemed rather related to euploid embryos from first-degree cousins (PSR = 0.80 versus 0.98 in second-degree cousins, NS). Euploid embryos from NCS presented a PSR of 0.96, with 49.1% XY versus 50.9% XX blastocysts (OR 0.98, 95% CI 0.79-1.22; NS). Significant differences in prevalence of euploidy of specific chromosomes were encountered between CS and NCS.

CONCLUSIONS

The primary sex ratio was generally similar in expanded blastocysts from consanguine and non-consanguine couples, with a slight decrease in primary sex ratio of euploid blastocysts from consanguine couples.

Analysis of a preimplantation genetic test for aneuploidies in 893 screened blastocysts using KaryoLite BoBs: a single-centre experience

INTRODUCTION

Does euploidy of trophectoderm (TE) biopsies correlate with conventional blastocyst morphological, maternal age and implantation potential?

METHODS

This is a one-centre, retrospective, observational study.

RESULTS

Eight hundred and ninety-three blastocysts were biopsied; 57.73% were euploid. The euploidy rate was found to be significantly higher for the embryos with good morphology of inner cell mass (ICM) and TE. Between ICM and TE morphology variables, TE was more predictive of the euploidy rate. When broken down into different age groups, the percentage of good morphology embryos remained similar across all age groups, while the percentage of euploid embryos dropped with increasing age. These results suggest that the correlation between blastocyst morphology and ploidy status was present but poor. Faster growing day 5 blastocysts showed a significantly higher euploidy rate than slower growing day 6 or 7 blastocysts. The number of good-quality blastocysts per cycle, euploid blastocysts per cycle and the euploidy rate were strongly associated with maternal age. A trend towards an increased implantation rate was found with euploid embryo transfers compared to the control group without preimplantation genetic test for aneuploidies (PGT-A).

CONCLUSIONS

Blastocyst morphology, rate of development and maternal age were found to be significantly associated with euploidy rate. There is a trend that suggests PGT-A may help to improve the pregnancy rate, but it is not statistically different, and therefore, PGT-A remains an unproven hypothesis. Due to the limitation of a small size of the control group, further studies with more data are needed.

Assisted reproductive technology induces different secondary sex ratio: parental and embryonic impacts

BACKGROUND

Assisted reproduction technology (ART) has advanced significantly, raising concerns regarding its impact on the secondary sex ratio (SSR), which is the sex ratio at birth in offspring. This study aimed to explore factors affecting SSR in singletons, singletons from twin gestation, and twins from twin gestation within the context of ART.

METHODS

A retrospective analysis was conducted on data from 8335 births involving 6,223 couples undergoing ART. Binary logistic regression assessed relationships between parental and embryonic factors and SSR in singletons and singletons from twin gestation. Multinomial logistic regression models were utilized to identify factors influencing SSR in twins from twin gestation.

RESULTS

Secondary infertility (OR = 1.164, 95% CI: 1.009-1.342), advanced paternal age (OR = 1.261, 95% CI: 1.038-1.534), and blastocyst embryo transfer (OR = 1.339, 95% CI: 1.030-1.742) were associated with an increased SSR, while frozen embryo transfer (FET) showed a negative association with SSR (OR = 0.738, 95% CI: 0.597-0.912) in singletons. A longer duration of gonadotropin (Gn) usage reduced SSR in singletons (OR = 0.961, 95% CI: 0.932-0.990) and singletons from twin gestation (OR = 0.906, 95% CI: 0.838-0.980). In singletons from twin gestation, male-induced infertility (OR = 2.208, 95% CI: 1.120-4.348) and higher Gn dosage (OR = 1.250, 95% CI: 1.010-1.548) were significantly associated with an increased SSR. Women aged > 35 years and intracytoplasmic sperm injection (ICSI) were associated with lower SSR (OR = 0.539, 95% CI: 0.293-0.990 and OR = 0.331, 95% CI: 0.158-0.690, respectively). In twins from twin gestation, paternal age exceeded maternal age (OR = 0.682, 95% CI: 0.492-0.945) and higher Gn dosage (OR = 0.837, 95% CI: 0.715-0.980) were associated with a higher proportion of male twins. Cleavage stage transfer (OR = 1.754, 95% CI: 1.133-2.716) resulted in a higher percentage of boy-girl twins compared to blastocyst transfer.

CONCLUSION

This study demonstrates the complex interplay of various factors in determining the SSR in ART, highlighting the importance of considering infertility type, paternal age, fertilization method, embryo transfer stage, and Gn use duration when assessing SSR. Nevertheless, further research with a large sample size is necessary to confirm and expand upon the findings of this study.

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.

Who's afraid of the X? Incorporating the X and Y chromosomes into the analysis of DNA methylation array data

BACKGROUND

Many human disease phenotypes manifest differently by sex, making the development of methods for incorporating X and Y-chromosome data into analyses vital. Unfortunately, X and Y chromosome data are frequently excluded from large-scale analyses of the human genome and epigenome due to analytical complexity associated with sex chromosome dosage differences between XX and XY individuals, and the impact of X-chromosome inactivation (XCI) on the epigenome. As such, little attention has been given to considering the methods by which sex chromosome data may be included in analyses of DNA methylation (DNAme) array data.

RESULTS

With Illumina Infinium HumanMethylation450 DNAme array data from 634 placental samples, we investigated the effects of probe filtering, normalization, and batch correction on DNAme data from the X and Y chromosomes. Processing steps were evaluated in both mixed-sex and sex-stratified subsets of the analysis cohort to identify whether including both sexes impacted processing results. We found that identification of probes that have a high detection p-value, or that are non-variable, should be performed in sex-stratified data subsets to avoid over- and under-estimation of the quantity of probes eligible for removal, respectively. All normalization techniques investigated returned X and Y DNAme data that were highly correlated with the raw data from the same samples. We found no difference in batch correction results after application to mixed-sex or sex-stratified cohorts. Additionally, we identify two analytical methods suitable for XY chromosome data, the choice between which should be guided by the research question of interest, and we performed a proof-of-concept analysis studying differential DNAme on the X and Y chromosome in the context of placental acute chorioamnionitis. Finally, we provide an annotation of probe types that may be desirable to filter in X and Y chromosome analyses, including probes in repetitive elements, the X-transposed region, and cancer-testis gene promoters.

CONCLUSION

While there may be no single "best" approach for analyzing DNAme array data from the X and Y chromosome, analysts must consider key factors during processing and analysis of sex chromosome data to accommodate the underlying biology of these chromosomes, and the technical limitations of DNA methylation arrays.

Sex ratio imbalance following blastocyst transfer is associated with ICSI but not with IVF: an analysis of 14,892 single embryo transfer cycles

PURPOSE

Assisted reproductive technology (ART) has an impact on secondary sex ratio (SSR), which is seemed to be elevated after blastocyst transfer (BT) but decreased following ICSI procedure. We aim to assess whether the higher SSR associated with BT could be influenced by fertilization method used.

METHODS

All consecutive IVF/ICSI cycles (fresh and frozen) involving single embryo transfer (SET) resulting in a live birth between 2015 and 2019 were retrospective analyzed. Logistic regression was used to model the effect on the SSR of maternal and specific ART characteristics.

RESULTS

Six thousand nine hundred twenty-two women were included with the crude SSR of 54.8%. The impact of BT on SSR is influenced by the fertilization method used. After adjustment for potential confounders, the SSR in the ICSI BT group was significantly higher when compared to ICSI cleavage-stage embryo SET (aOR 1.24; 95% CI 1.10-1.40, P < 0.001). However, this effect was not detected among SBT with IVF treatment (aOR 1.04; 95% CI 0.97-1.12, P = 0.260). Assessing blastocyst morphological parameters, high trophectoderm quality was significantly associated with elevated SSR (aOR 1.76, 95% CI 1.34-2.31 [A vs. C], and aOR 1.28, 95% CI 1.14-1.44 [B vs. C]). No significant difference was shown in expansion, inner cell mass, or days of blastocyst formation between male and female blastocysts.

CONCLUSIONS

The impact of BT on SSR could be influenced by the fertilization method used. The higher SSR was observed after BT with ICSI procedures but not with IVF. Interpretation of the findings is limited by the potential for selection and confounding bias.

Sex ratio of infants born through in vitro fertilization and embryo transfer: Results of a single-institution study and literature review

Objective:

The possible effects of Assisted Reproductive Technology (ART) on sex ratio at birth are extremely significant. This study aimed to determine whether ART affects the sex ratio of infants born through in vitro fertilization and embryo transfer (IVF-ET).

Materials and Methods:

We ran this retrospective study on 290 singleton infants born following IVF-ET from February 2014 to August 2018 at a single institution. We compared the sex ratios of these infants with respect to insemination versus intracytoplasmic sperm injection (ICSI), early-cleavage embryo versus blastocyst transfer, fresh versus frozen-thawed embryo transfer and normal sperm versus asthenospermia.

Results:

There were no significant differences in the sex ratio with respect to the fertilization method, transfer time, fresh embryo or frozen-thawed embryo transfer. In addition, the multiple logistic regression analysis revealed that these factors did not significantly affect the sex ratio.

Conclusions:

Our study indicated that the differences in the fertilization method transfer time and sperm motility rate did not affect the sex ratio of IVF live births. However, with increasing numbers of ICSI and blastocyst transfer cycles, factors possibly affecting the sex ratio need to be further investigated.

Sex Differences Are Here to Stay: Relevance to Prenatal Care

Sex differences exist in the incidence and presentation of many pregnancy complications, including but not limited to pregnancy loss, spontaneous preterm birth, and fetal growth restriction. Sex differences arise very early in development due to differential gene expression from the X and Y chromosomes, and later may also be influenced by the action of gonadal steroid hormones. Though offspring sex is not considered in most prenatal diagnostic or therapeutic strategies currently in use, it may be beneficial to consider sex differences and the associated mechanisms underlying pregnancy complications. This review will cover (i) the prevalence and presentation of sex differences that occur in perinatal complications, particularly with a focus on the placenta; (ii) possible mechanisms underlying the development of sex differences in placental function and pregnancy phenotypes; and (iii) knowledge gaps that should be addressed in the development of diagnostic or risk prediction tools for such complications, with an emphasis on those for which it would be important to consider sex.

The Gender Gap in the Diagnostic-Therapeutic Journey of the Infertile Couple

Medical procreation impairs both the biological and psychological lives of couples. However, male and female attitudes to infertility are different and require a different approach during the IVF journey. Thus, the gender impact assessment (GIA) method was used to analyse original studies present in the literature. We found some gender-related differences and, subsequently, possible outcomes of intervention to improve healthy reproduction management and prevent infertility. In particular, it became apparent that there was the need for an in-depth male infertility assessment and a gender-specific follow-up.

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.

Associated factors of secondary sex ratio of offspring in assisted reproductive technology: a cross-sectional study in Jilin Province, China

Background

The aim of this study was to determine the secondary sex ratio (SSR) of offspring in assisted reproduction technology (ART) in Jilin Province, China, and to analyse the influencing factors associated with SSR.

Methods

A cross-sectional study of 3833 babies including singletons and twins born to 2990 couples treated by ART between May 2011 and December 2018 was performed.

Results

The main outcomes of this study were that the SSR of ART babies in Jilin Province was 50.64% and the SSR was associated with fertilization methods (p < 0.05). Comparing to in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) (OR = 0.808, 95%CI: 0.681–0.958) decreased the percentage of male babies.

Conclusions

This study suggests that the SSR of ART births in Jilin Province was lower than the normal level and ICSI had a significant effect on SSR. Though we need more samples to study in the future, we still need to think about the impact of ICSI on SSR in ART.

Does the sex ratio of singleton births after frozen single blastocyst transfer differ in relation to blastocyst development?

PURPOSE

To investigate the associations between blastocyst development and the sex ratio (male:female) among singleton live births resulting from single-blastocyst frozen embryo transfer (FET) cycles.

METHODS

Patients with singleton live births following the first autologous single FET of non- preimplantation genetic testing (PGT) blastocysts in a single reproductive medicine department between January 2015 and February 2019 were included in this retrospective study. The primary outcome measure was the singleton sex ratio. Multivariable logistic regression models were used to estimate the associations between blastocyst quality and singleton sex ratio after adjustment for some potential confounders.

RESULTS

There were 638 high-quality and 572 poor-quality single blastocyst FETs, and the blastocysts were conceived via 855 IVF and 355 ICSI treatments. A total of 1210 singleton live births were assessed. High-quality single blastocyst FET resulted in a significantly higher sex ratio than did poor-quality single blastocyst FET (60% vs. 49.7%, P < 0.001). The infertility cause was not associated with sex ratio among singleton live births (P = 0.537). The results of a multivariate analysis revealed that a high-quality blastocyst has a 150% higher probability of being male than a poor-quality blastocyst (adjusted odds ratio (aOR) 1.57; 95% CI 1.24-2, P < 0.001). Among the three blastocyst morphological parameters, Grade B trophectoderm was significantly associated with a higher sex ratio than Grade C (aOR 1.71; 95% CI 1.33-2.21. P < 0.001). Neither expansion degree nor inner cell mass degree were significantly associated with the singleton sex ratio.

CONCLUSIONS

A single high-quality blastocyst FET has a higher chance of resulting in a male infant than a female infant. The results demonstrate that grade B trophectoderm confers benefits in improving the implantation potential of male blastocysts.

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.

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.

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.

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.

Time-lapse variables and embryo gender: a retrospective analysis of 81 live births obtained following minimal stimulation and single embryo transfer

PURPOSE

The purpose of this study was to determine which morphokinetic variables are related to embryo gender in a cohort of consecutive live births obtained through single blastocyst transfer following mild ovarian stimulation.

METHODS

Eighty-one live births (49 % of them females) from successfully treated, consecutive infertile patients (maternal age 36.9 ± 3.8 years, range 28-46) who underwent minimal ovarian stimulation, prolonged embryo culture in a time-lapse monitoring (TLM) incubator and elective single blastocyst transfers during 2012-2014. Early (PNf, t2-t9, cc2a, b, s2, s3) and late (tM, tSB, tfullB, texpB1, and texpB2) morphokinetic variables were scored according to published consensus criteria and were normalized to the time of pronuclear fading. For each variable, the ranges with the highest proportion of female embryos (optimal range) were determined by detailed examination of histograms.

RESULTS

Female embryo gender was associated both with late cleavage (t8), morula (tM), and blastocyst stage morphokinetic variables. The strongest associations (adjusted ORs, 7.0-7.8) were found for late, expanded stage blastocyst parameters; tfullB, texpB1, and texpB2. The proportion of female embryos was 69-71 and 25-26 % inside and outside of the optimal ranges, respectively. This allowed to predict 74-78 % of them, increasing their proportion by 57 % compared to the average.

CONCLUSIONS

Although the sample size of our cohort was limited, our findings suggest that several expanded blastocyst stage morphokinetic parameters are associated with female embryo gender. If confirmed on a larger sample these could be potentially used to increase the proportion of female embryos among non-invasively selected blastocysts following single embryo transfer.

Assisted reproductive outcomes of male cancer survivors

PURPOSE

The objective of our study was to evaluate the reproductive outcome of male cancer survivors treated with intracytoplasmic sperm injection (ICSI) using cryopreserved sperm and compare it with the same treatment in non-cancer males.

METHODS

We retrospectively analyzed database derived from cancer and non-cancer patients undergoing sperm cryopreservation from August 2008 to August 2012 at a university-based center. We evaluated the reproductive outcome of those cancer and non-cancer patients that had frozen sperm and returned subsequently to the clinic for assisted reproduction.

RESULTS

We studied 272 males with cancer and 296 infertile males. The most prevalent types of cancer in our cohort were lymphoma (25.3 %), testicular cancer (19.2 %), leukemia (7.3 %), and other malignancies including sarcoma, gastrointestinal, and central nervous system malignancies (48.2 %). The use rate of cryopreserved sperm was 10.7 % for cancer patients and 30.7 % for non-cancer patients. The mean age of males with cancer who returned to the clinic for fertility treatment was 36.7 ± 6 years, and the diagnoses were testis cancer (43.4 %), lymphoma (36.9 %), leukemia (13 %), and other malignancies (6.7 %). Live birth rate of the cancer cohort was 62.1 %, which was higher than that of the normospermic non-cancer population (p < 0.0047).

CONCLUSIONS

The use rate of cryopreserved sperm from oncofertility preservation cases is at around 10 %. The live birth rate using assisted reproductive technologies among these patients is at least comparable to that of the non-cancer population.

IMPLICATIONS FOR CANCER SURVIVORS

To our knowledge, this was the first comparative study of male cancer survivors treated with ICSI using cryopreserved sperm, which were compared to non-cancer males undergoing the same treatment. Male fertility preservation is a highly valued service that should be strongly encouraged prior to beginning cytotoxic cancer treatment. These results can help healthcare professionals in oncology to improve the quality of counseling on fertility preservation when managing young men with newly diagnosed cancer that require gonadotoxic treatment.

Effects of assisted reproductive technologies on human sex ratio at birth

OBJECTIVE

To investigate the effect of assisted reproductive technology (ART) treatments on the sex ratio of babies born.

DESIGN

Assessment of direct effects of assisted conception through retrospective data analysis on the progeny sex ratio of treated women in the United Kingdom.

SETTING

The study uses the anonymized register of the Human Fertilisation and Embryology Authority.

PATIENT(S)

A total of 106,066 babies of known gender born to 76,994 treated mothers and 85,511 treatment cycles between 2000 and 2010 in the United Kingdom.

INTERVENTION(S)

Intrauterine insemination, IVF, or intracytoplasmic sperm injection (ICSI).

MAIN OUTCOME MEASURE(S)

Sex ratio of babies born.

RESULT(S)

Intrauterine insemination, IVF, and ICSI lead to different sex ratios, highest after IVF (proportion male = mean 0.521 ± confidence interval 0.0056) and lowest under ICSI embryo transfer (0.493 ± 0.0031). In addition, for both ICSI and IVF, transferring embryos at a later stage (blastocyst) results in approximately 6% more males than after early cleavage-stage ET.

CONCLUSION(S)

Because the cumulative number of IVF babies born is increasing significantly in Britain and elsewhere, more research is needed into the causes of gender bias after ART and into the public health impact of such gender bias of offspring born observed on the rest of the population.

The effect on human sex ratio at birth by assisted reproductive technology (ART) procedures--an assessment of babies born following single embryo transfers, Australia and New Zealand, 2002-2006

OBJECTIVE

To assess the effect on the human sex ratio at birth by assisted reproductive technology (ART) procedures.

DESIGN

Retrospective population-based study.

SETTING

Fertility clinics in Australia and New Zealand.

POPULATION

The study included 13,368 babies by 13,165 women who had a single embryo transfer (SET) between 2002 and 2006.

METHODS

Logistic regression was used to model the effect on the sex ratio at birth of ART characteristics [in vitro fertilisation (IVF) or intracytoplasmic sperm insemination (ICSI) SET, cleavage-stage or blastocyst SET, and fresh or thawed SET] and biological characteristics (woman's and partner's age and cause of infertility).

MAIN OUTCOME MEASURES

Proportion of male births.

RESULTS

The crude sex ratio at birth was 51.3%. Individual ART procedures had a significant effect on the sex ratio at birth. More males were born following IVF SET (53.0%) than ICSI SET (50.0%), and following blastocyst SET (54.1%) than cleavage-stage SET (49.9%). For a specific ART regimen, IVF blastocyst SET produced more males (56.1%) and ICSI cleavage-stage SET produced fewer males (48.7%).

CONCLUSIONS

The change in the sex ratio at birth of SET babies is associated with the ART regimen. The mechanism of these effects remains unclear. Fertility clinics and patients should be aware of the bias in the sex ratio at birth when using ART procedures.

Influence of embryo sex on development to the blastocyst stage and euploidy

OBJECTIVE

To compare the prevalence of blastocyst development and euploidy in XX versus XY embryos.

DESIGN

Retrospective cohort study.

SETTING

Boston IVF, a large university-affiliated reproductive medicine practice.

PATIENT(S)

All patients who underwent their first preimplantation genetic screening cycle between January 1, 2006, and December 31, 2007.

INTERVENTION(S)

In vitro fertilization and preimplantation genetic screening.

MAIN OUTCOME MEASURE(S)

Proportion of embryos that developed to the blastocyst stage by day 5 and prevalence of euploidy for chromosomes 8, 13, 14, 15, 16, 17, 18, 20, 21, and 22 in XX versus XY embryos.

RESULT(S)

Seven hundred fifty-eight embryos from 138 cycles in 138 patients were analyzed. Three hundred sixty-six (48%) were XX, and 392 (52%) were XY. XX and XY embryos were equally likely to develop to the blastocyst stage by day 5 and were equally likely to be euploid for the analyzed chromosomes.

CONCLUSION(S)

Our data suggest that extending embryo culture to day 5 does not lead to sex selection and that euploidy and aneuploidy are not sex dependent.