Culture media affect sex after IVF treatment-a detailed analysis of explanatory variables

PURPOSE

The purpose of this study was to provide a detailed analysis of clinical and laboratory factors associated with skewed secondary sex ratio (SSR) after ART.

METHOD

Retrospective cohort study of embryos resulting in live births, from frozen and fresh single blastocyst transfers. Embryos were cultured in either G-TL (n = 686) or Sage media (n = 685). Data was analyzed using a multivariate logistic regression model and a mixed model analysis.

RESULTS

Significantly more male singletons were born after culture in Sage media compared to G-TL media (odds ratio (OR) 1.34, 95% CI (1.05, 1.70), P = 0.02). Inner cell mass grade B vs A (OR 1.36 95% CI (1.05, 1.76), P = 0.02) and one previous embryo transfer (OR 1.49, 95% CI (1.03, 2.16), P = 0.03) were associated with a significantly higher probability of male child at birth. Factors associated with a reduced probability of male child were expansion grade 3 vs 5 (OR 0.66, 95% CI (10.45, 0.96), P = 0.03) and trophectoderm grade B vs A (OR 0.57, 95% CI (0.44, 0.74), P = 0.00). Male embryos developed significantly faster in Sage media compared to G-TL media for the stages of blastocyst (- 1.12 h, 95% CI (- 2.12, - 0.12)), expanded blastocyst (- 1.35 h, 95% CI (- 2.34, - 0.35)), and hatched blastocyst (- 1.75 h, 95% CI (- 2.99, - 0.52)).

CONCLUSION

More male children were born after culture in Sage media compared to G-TL media. Male embryo development was affected by culture media. Our observations suggest that culture media impact male embryo quality selectively, thus potentially favoring the selection of male embryos.

Association between the body mass index of women undergoing IVF and the gender of the offspring

RESEARCH QUESTION

Is there an association between women's body mass index (BMI) and the gender of offspring generated from fresh or frozen-thawed embryo transfer (FET) cycles?

DESIGN

Between 2018 and 2021, 2670 cycles were performed, comprising 786 fresh embryo transfers and 1884 FET cycles. The study analysed the relationship between the BMI of women undergoing IVF and the sex of the newborn and the male-to-female live birth ratio (secondary sex ratio [SSR]).

RESULTS

After 2670 single-embryo transfers, 483 (50.31%) male and 477 (49.69%) female infants were born, with an SSR of 101.3. In the fresh embryo transfer group, the SSR ranged from 350 (95% CI 82.67-1481.65) in underweight women (although this was based on very small numbers) to 109.7 (95% CI 67.73-176.61) in overweight women, while in the FET group, SSR values varied correspondingly from 130.8 (95% CI 64.47-265.26) to 63.0 (95% CI 46.02-86.24). Results from Bayesian multinomial logistic regression showed that for each unit increase in BMI within the fresh embryo transfer group, the odds of a boy's birth decreased by 6% (odds ratio [OR] 0.94, 95% CI 0.90-0.99) and the odds of a girl's birth by 5% (OR 0.95, 95% CI 0.90-0.99). Within the FET cohort, the odds of a boy's birth decreased by 4% (OR 0.96, 95% CI 0.92-0.99), while the odds of a girl's birth increased by 3% (OR 1.03, 95% CI 1.00-1.06).

CONCLUSIONS

An increase in BMI is associated with the birth of fewer boys in fresh or frozen embryo transfer cycles, and a significant increase in the birth of girls in FET cycles.

Culture medium is associated with the risks of placenta previa and macrosomia in pregnancies after in vitro fertilization

PURPOSE

The culture medium plays an important role in embryonic development and subsequent pregnancy outcomes of in vitro fertilization (IVF) cycles. The sequential culture media of Vitrolife and Cook are the two most commonly used reagents in China. This study aimed to assess their effects on IVF success rates, obstetric outcomes and neonatal outcomes.

METHODS

This was a retrospective cohort study on 6352 patients undergoing first IVF attempts between January 2018 and December 2019, resulting in 3153 clinical pregnancies, 2646 live births, and 2668 babies. Patients were grouped according to the culture media they used. There were 4680 patients in the Vitrolife group and 1672 patients in the Cook group. The primary outcome measures were maternal and neonatal outcomes. ANOVA and Chi-square tests were used for statistical comparison, and multivariate logistic regression and multivariate general linear model were used to adjust for potential confounders.

RESULTS

The rates of live birth, clinical pregnancy, monozygotic twins, miscarriage, and ectopic pregnancy were all comparable between the groups of Vitrolife and Cook. The incidence of placenta previa was higher in the Vitrolife group [4.86 vs. 3.09%, adjusted odds ratio = 2.048 (1.146-3.657)]. The incidence of macrosomia was higher in the Cook group [7.51 vs. 5.39%, adjusted odds ratio = 1.445 (1.010-2.069)].

CONCLUSION

The culture media of Vitrolife and Cook are comparably effective in IVF success. Vitrolife is associated with a higher risk of placenta previa, while Cook is associated with a higher risk of macrosomia.

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.

Night shift work undertaken by women and fertility treatment interact to increase prevalence of urogenital anomalies in children

OBJECTIVE

To investigate the role of maternal night shift work in occurrence of urogenital anomalies in offspring, considering a possible interaction with mode of conception.

METHODS

A population-based cohort comprising births in South Australia (1986-2002) was produced via linkage of fertility clinic records, perinatal and birth defects data. This study concerned first births to women in paid employment (n=98 103). Potential exposure to night shift was imputed by applying a job-exposure matrix to recorded occupation. Associations were examined using logistic regression, first for nurses and other night shift workers separately, then combined. An interaction term for night shift work and mode of conception was included in all models, while adjusting for covariates.

RESULTS

Associations were similar for nurses and other night shift workers, although only statistically significant for the former when considered separately. A multiplicative interaction was supported: for natural conceptions, maternal night shift work was not associated with offspring urogenital anomalies (OR=0.99, 95% CI 0.84 to 1.15); where a birth arose from fertility treatment, urogenital anomalies were significantly higher among births to all night shift workers compared with day workers (OR=2.07, 95% CI 1.20 to 3.55). This was not due to differences in the type of fertility treatment received.

CONCLUSIONS

Women in occupations that probably involved night shift did not have offspring with increased prevalence of urogenital anomalies if they conceived naturally. When night shift workers conceived with fertility treatment, the prevalence of urogenital anomalies was elevated. Possibly these women had the greatest exposure to night shift work, or least tolerance for this work schedule, or heightened sensitivity to hormonal aspects of fertility treatment.

Ovarian Hyperstimulation Syndrome Is Associated with a High Secondary Sex Ratio in Fresh IVF Cycles with Cleavage-Stage Embryo Transfer: Results for a Cohort Study

The sex ratio at birth is defined as the secondary sex ratio (SSR). Ovarian hyperstimulation syndrome (OHSS) is a serious and iatrogenic complication associated with controlled ovarian stimulation (COS) during assisted reproductive technology (ART) treatments. It has been hypothesized that the human SSR is partially controlled by parental hormone levels around the time of conception. Given the aberrant hormonal profiles observed in patients with OHSS, this retrospective study was designed to evaluate the impact of OHSS on the SSR. In this study, all included patients were divided into 3 groups: non-OHSS (n=2777), mild OHSS (n=644), and moderate OHSS (n=334). Our results showed that the overall SSR for the study population was 1.033. The SSR was significantly increased in patients with moderate OHSS (1.336) compared to non-OHSS patients (1.002) (p=0.048). Subgroup analyses showed that increases in the SSR in patients with moderate OHSS were observed in the IVF group (1.323 vs 1.052; p=0.043), but not in the ICSI groups (1.021 vs 0.866; p=0.732). In addition, the elevated serum estradiol (E2) and progesterone (P4) levels in OHSS patients were not associated with SSR. In this study, for the first time, we report that a high SSR is associated with OHSS in patients who received fresh IVF treatments. The increases in SSR in OHSS patients are not attributed to the high serum E2 and P4 levels. Our findings may make both ART clinicians and patients more aware of the influences of ART treatments on the SSR and allow clinicians to counsel patients more appropriately.

Secondary sex ratio in assisted reproduction: an analysis of 1 376 454 treatment cycles performed in the UK

STUDY QUESTION

Does ART impact the secondary sex ratio (SSR) when compared to natural conception?

SUMMARY ANSWER

IVF and ICSI as well as the stage of embryo transfer does impact the overall SSR.

WHAT IS KNOWN ALREADY

The World Health Organization quotes SSR for natural conception to range between 103 and 110 males per 100 female births.

STUDY DESIGN SIZE DURATION

A total of 1 376 454 ART cycles were identified, of which 1 002 698 (72.8%) cycles involved IVF or ICSI. Of these, 863 859 (85.2%) were fresh cycles and 124 654 (12.4%) were frozen cycles. Missing data were identified in 14 185 (1.4%) cycles.

PARTICIPANTS/MATERIALS SETTING METHODS

All cycles recorded in the anonymized UK Human Fertilisation and Embryology Authority (HFEA) registry database between 1991 and 2016 were analysed. All singleton live births were included, and multiple births were excluded to avoid duplication.

MAIN RESULTS AND THE ROLE OF CHANCE

The overall live birth rate per cycle for all IVF and ICSI treatments was 26.2% (n = 262 961), and the singleton live birth rate per cycle was 17.1% (n = 171 399). The overall SSR for this study was 104.0 males per 100 female births (binomial exact 95% CI: 103.1-105.0) for all IVF and ICSI cycles performed in the UK recorded through the HFEA. This was comparable to the overall SSR for England and Wales at 105.3 males per 100 female births (95% CI: 105.2-105.4) from 1991 to 2016 obtained from the Office of National Statistics database. Male predominance was seen with conventional insemination in fresh IVF treatment cycles (SSR 110.0 males per 100 female births; 95% CI: 108.6-111.5) when compared to micro-injection in fresh ICSI treatment cycles (SSR 97.8 males per 100 female births; 95% CI: 96.5-99.2; odds ratio (OR) 1.16, 95% CI 1.12-1.19, P < 0.0001), as well as with blastocyst stage embryo transfers (SSR 104.8 males per 100 female births; 95% CI: 103.5-106.2) when compared to a cleavage stage embryo transfer (SSR 101.2 males per 100 female births; 95% CI: 99.3-103.1; OR 1.03, 95% CI 1.01-1.06, P = 0.011) for all fertilization methods.

LIMITATIONS REASONS FOR CAUTION

The quality of the data relies on the reporting system. Furthermore, success rates through ART have improved since 1991, with an increased number of blastocyst stage embryo transfers.

WIDER IMPLICATIONS OF THE FINDINGS

This is the largest study to date evaluating the impact of ART on SSR. The results demonstrate that, overall, ART does have an impact on the SSR when assessed according to the method of fertilization (ICSI increased female births while IVF increased males). However, given the ratio of IVF to ICSI cycles at present with 60% of cycles from IVF and 40% from ICSI, the overall SSR for ART closely reflects the population SSR for, largely, natural conceptions in England and Wales.

STUDY FUNDING/COMPETING INTERESTS

The study received no funding. C.M.B. is a member of the independent data monitoring group for a clinical endometriosis trial by ObsEva. He is on the scientific advisory board for Myovant and medical advisory board for Flo Health. He has received research grants from Bayer AG, MDNA Life Sciences, Volition Rx and Roche Diagnostics as well as from Wellbeing of Women, Medical Research Council UK, the NIH, the UK National Institute for Health Research and the European Union. He is the current Chair of the Endometriosis Guideline Development Group for ESHRE and was a co-opted member of the Endometriosis Guideline Group by the UK National Institute for Health and Care Excellence (NICE). I.G. has received research grants from Wellbeing of Women, the European Union and Finox.

TRIAL REGISTRATION NUMBER

Not applicable.

Proteomic profile of sex-sorted bull sperm evaluated by SWATH-MS analysis

The identification of distinct proteins present on the membrane of spermatozoa with X and Y chromosomes allows the development of immuno-sexing techniques. The aim of this study, therefore, was to use mass spectrometry to analyze the protein profile of sperm previously categorized using flow cytometry into X or Y-bearing semen pools. Sex-sorted sperm samples (n = 6 X and n = 6 Y) were used. Proteins were extracted and analyzed by mass spectrometry using data independent acquisition (DIA). The data were searched against taxonomy Bos taurus in the Swiss Prot database. In total, 459 protein groups were identified. Of these, eight proteins were in differential abundances between the X- and Y-bearing sperm population. Among the major proteinsdetected, EF-hand domain-containing protein 1, a protein involved in embryonic development, is more abundant in Y-bearing spermatozoa. In addition, proteins FUN14, domain-containing protein 2, NADH dehydrogenase [ubiquinone] iron-sulfur protein 7 mitochondrial, cytochrome C oxidase subunit 2, acetyl -CoA carboxylase type beta were more abundant in X-bearing sperm. In conclusion, there were differences in abundance of proteins between X- and Y-bearing bull spermatozoa. This fact, may contribute to future studies related to sperm physiology and possibility development of immuno-sexing techniques.

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.

A review of the established and suspected causes of variations in human sex ratio at birth

The human sex ratio (proportion male) at birth (SRB) varies with many variables. Some of this variation has an established proximate cause. For instance, low SRB (more females) at birth are associated with various forms of stressful events or circumstances during or prior to pregnancy. These low SRB are almost certainly mainly caused by maternal-stress-induced male foetal loss. Other types of SRB variation are thought to be caused by hormonal variation in either or both parents around the time of conception. One or other of these two types of proximate cause seems to be responsible for most of the established variation of SRB. This will be illustrated here in respect of some selected forms of SRB variation. It seems likely that a clarification of the hormonal causes of SRB variation will also help explain the striking (apparent) inconsistencies in the results of reported tests of the influential Trivers-Willard hypothesis. It is further proposed that an appreciation of the evidence that parental hormones influence SRB may enhance understanding of several important pathologies (hepatitis B, toxoplasmosis, testicular cancer, prostate cancer and autism).

Sex ratio at birth is associated with type 1 diabetes characteristics

AIMS

To assess the association between maternal diabetes characteristics and sex ratio at birth (SRB) in women with type 1 diabetes mellitus.

METHODS

We performed a case-control study. The study subjects were infants born alive to women with type 1 diabetes and singleton pregnancies. Cases and controls were defined as male and female newborns, respectively. SRB was analysed according to diabetes-related characteristics adjusting in a logistic regression analysis for maternal characteristics known to affect SRB in the general population.

RESULTS

The observed SRB (238 males/468 live births = 0.509) did not differ from the expected. In the logistic regression analysis, SRB was significantly associated with three diabetes characteristics: (1) diabetes duration, with odds ratios (ORs) for a live male newborn = 1.22 (95 % confidence interval (CI), 0.66-2.24 for ≤5 years, OR 2.79 (95 % CI 1.36-5.74) for >20 years; (2) mean first-trimester glycated haemoglobin, with OR 1.98 (95 % CI 1.09-3.62) for ≤6.7 % (50 mmol/mol) and OR 2.61 (95 % CI 1.16-5.85) for >8.2 % (66 mmol/mol) and (3) mean first-trimester insulin dose, with OR 0.70 (95 % CI 0.36-1.38) for ≤0.5 IU/kg/day and OR 0.18 (95 % CI 0.05-0.59) for >1.0 IU/kg/day.

CONCLUSIONS

We conclude that SRB in this cohort is independently associated with three diabetes characteristics. These associations are to be confirmed.

The day of embryo transfer affects delivery rate, birth weights, female-to-male ratio, and monozygotic twin rate

OBJECTIVE

To compare the reproductive outcomes between the transfer of cleavage-stage embryos and blastocysts in two different age groups of patients. The reproductive capacity of women decreases by age. This decrease in capacity is directly related to a lower ovarian reserve and errors in the meiotic spindle of the oocyte, which increase chromosomal abnormalities and the formation of aneuploidy embryos with lower chances of implantation.

MATERIALS AND METHODS

A total of 1400 intracytoplasmic sperm injection cycles were analyzed. The study patients were divided into two age groups [aged < 36 years (Group I) and aged ≧ 36 years (Group II)]. The groups were subdivided according to the day of embryo transfer (ET)-Day 3 (ET3) and Day 5 (ET5).

RESULTS

In both age groups, transfer of blastocysts resulted in a higher clinical pregnancy rate and deliveries. An increased twin birth rate was observed in patients who were younger than 36 years on both transfer days compared with those who were older than 36 years of age. There was an elevated percentage of newborn males on ET5 in both age groups. Monozygotic twinning (MZT) rate was observed only among younger patients (<36 years of age), specifically on ET5 compared with ET3. There was no significant difference in the mean birth weight of singleton and twins between the ET3 and ET5 subgroups in the younger group of patients except for the triplets who were significantly heavier in the ET5 group compared with the older group (≧36 years of age) where significant difference was found only on the mean birth weight of singleton.

CONCLUSION

The study suggests that if a blastocyst can be obtained in patients of advanced age (≧36 years), it improves their baby take-home rates. Younger patients (aged < 36 years) should undergo elective single blastocyst transfers to reduce multiple pregnancy rates.

Phenotypic developmental plasticity induced by preincubation egg storage in chicken embryos (Gallus gallus domesticus)

The developing chicken blastoderm can be temporarily maintained in dormancy below physiological zero temperature. However, prolonged preincubation egg storage impairs normal morphological and physiological development of embryos in a potential example of fetal programming (in this case, “embryonic programming”). We investigated how preincubation egg storage conditions (temperature, duration, hypoxia, and hypercapnia) affects viability, body mass, and physiological variables and functions in day 15 chicken embryos. Embryo viability was impaired in eggs stored for 2 and 3 weeks, with the effects greater at 22°C compared to 15°C. However, embryo size was reduced in eggs stored at 15°C compared with 22°C. Phenotypic change resulting from embryonic programming was evident in the fact that preincubation storage at 15°C diminished hematocrit (Hct), red blood cell concentration ([RBC]), and hemoglobin concentration ([Hb]). Storage duration at 15°C more severely affected the time course (2, 6, and 24 h) responses of Hct, [RBC], and [Hb] to progressive hypoxia and hypercapnia induced by submersion compared with storage duration at 22°C. The time‐specific regulation of acid–base balance was changed progressively with storage duration at both 22 and 15°C preincubation storages. Consequently, preincubation egg storage at 22°C resulted in poor viability compared with eggs stored at 15°C, but size and physiological functions of embryos in eggs stored for 1–2 weeks were worse in eggs stored in the cooler than stored under room conditions. Avian eggs thus prove to be useful for examining developmental consequences to physiology of altered preincubation thermal environment in very early stages of development (embryonic programming).

Responses of bovine early embryos to S-adenosyl methionine supplementation in culture

AIM

There is a growing concern about the potential adverse effects of high dose folic acid (FA) supplementation before and during pregnancy. FA metabolism generates S-adenosyl methionine (SAM) which is an important cofactor of epigenetic programming. We sought to assess the impact of a large dose of SAM on early embryo development.

MATERIALS & METHODS

In vitro cultured bovine embryos were treated with SAM from the eight-cell stage to the blastocyst stage. In addition to the phenotype, the genome-wide epigenetic and transcription profiles were analyzed.

RESULTS

Treatment significantly improved embryo hatching and caused a shift in sex ratio in favor of males. SAM caused genome-wide hypermethylation mainly in exonic regions and in CpG islands. Although differentially expressed genes were associated with response to nutrients and developmental processes, no correspondence was found with the differentially methylated regions, suggesting that cellular responses to SAM treatment during early embryo development may not require DNA methylation-driven changes.

CONCLUSION

Since bovine embryos were not indifferent to SAM, effects of large-dose FA supplements on early embryonic development in humans cannot be ruled out.