Fetal sex and very preterm birth

The sex ratio of singleton and twin delivery offspring in assisted reproductive technology in China

In order to evaluate the impact of assisted reproductive technology (ART) procedure and individual factors on the sex ratio of singletons and twins at birth after in vitro fertilization (IVF) and intra-cytoplasmic sperm injection (ICSI) treatment in China. We conducted a retrospective cohort study including patients undergoing their first cycle of IVF or ICSI with autologous oocytes from 2001 to 2015. A total of 7410 babies were born from 5832 women with 7410 live birth. The secondary sex ratio (SSR) in singletons was significantly higher than twins (53.97% vs. 50.89%, P = 0.009). The largest disparity was observed in 'thawed blastocyst embryos ICSI' subgroup that SSR was 59.84% in singletons and 42.45% in twins (P = 0.013). Blastocyst transfer was positively associated with elevated SSR when compared to cleavage stage embryos in singletons (Odds Ratio [OR] = 1.17, P < 0.001). In addition, paternal age was significantly associated with SSR (OR = 0.75, P = 0.014). While the decrease of SSR was significantly associated with ICSI when compared to IVF (OR = 0.61, P = 0.046) in twins. Blastocyst transfer increases SSR in comparing with cleavage stage embryos in singletons, while the use of ICSI reduces SSR in twins. Our findings offered important complement for better understanding the underlying determinant of SSR in ART offspring.

An analysis of variations of indications and maternal-fetal prognosis for caesarean section in a tertiary hospital of Beijing: A population-based retrospective cohort study

In recent decades, we have observed a remarkable increase in the rate of caesarean section (CS) in both developed and developing countries, especially in China. According to the World Health Organization (WHO) systematic review, if the increase in CS rate was between 10% and 15%, the maternal and neonatal mortality was decreased. However, above this level, increasing the rate of CS is no longer associated with reduced mortality. To date, no consensus has been reached on the main factors driving the cesarean epidemic. To reduce the progressively increasing rate of CS, we should find indications for the increasing CS rate. The aim of our study was to estimate the change of CS rate of Beijing Obstetrics and Gynecology Hospital and to find the variation of the indications.From January 1995 to December 2014, the CS rate of Beijing Obstetrics and Gynecology Hospital was analyzed. For our analysis, we selected 14,642 and 16,335 deliveries respectively that occurred during the year 2011 and 2014, to analyze the difference of indications, excluding incomplete data and miscarriages or termination of pregnancy before 28 weeks of gestation because of fatal malformations, intrauterine death, or other reasons.The average CS rate during the past 20 years was 51.15%. The highest caesarean delivery rate was 60.69% in 2002; however, the caesarean delivery rate declined to 34.53% in 2014. The obviously different indications were caesarean delivery on maternal request and previous CS delivery. The rate of CS due to maternal request in 2014 was decreased by 8.16% compared with the year 2011. However, the percentage of pregnancy women with a previous CS delivery increased from 9.61% to 20.42% in 3 years. Along with the decline of CS rate, the perinatal mortality and the rate of neonatal asphyxia decreased in 2014 compared with that in 2011.After a series of measures, the CS rate declined indeed. Compared with 2011, the perinatal mortality and the rate of neonatal asphyxia decreased in 2014. Caesarean delivery on maternal request (CDMR) cannot improve the maternal-fetal prognosis compared with the spontaneous vaginal delivery. With the releasing of China's 2 children policy, more CS will be implemented due to previous CS. There is a need for further research that evaluates interventions for increasing VBAC rates that target clinicians.

Impact of earthquakes on sex ratio at birth: Eastern Marmara earthquakes

OBJECTIVE

Previous reports suggest that maternal exposure to acute stress related to earthquakes affects the sex ratio at birth. Our aim was to examine the change in sex ratio at birth after Eastern Marmara earthquake disasters.

MATERIAL AND METHODS

This study was performed using the official birth statistics from January 1997 to December 2002 - before and after 17 August 1999, the date of the Golcuk Earthquake - supplied from the Turkey Statistics Institute. The secondary sex ratio was expressed as the male proportion at birth, and the ratio of both affected and unaffected areas were calculated and compared on a monthly basis using data from gender with using the Chi-square test.

RESULTS

We observed significant decreases in the secondary sex ratio in the 4th and 8th months following an earthquake in the affected region compared to the unaffected region (p= 0.001 and p= 0.024). In the earthquake region, the decrease observed in the secondary sex ratio during the 8th month after an earthquake was specific to the period after the earthquake.

CONCLUSION

Our study indicated a significant reduction in the secondary sex ratio after an earthquake. With these findings, events that cause sudden intense stress such as earthquakes can have an effect on the sex ratio at birth.

Placental abruption, offspring sex, and birth outcomes in a large cohort of mothers

OBJECTIVE

To investigate stillbirth, neonatal, and perinatal death outcomes in pregnancies complicated by placental abruption, according to fetal sex.

METHODS

We utilized maternally linked cohort data files of singleton live births to mothers diagnosed with placental abruption during the period 1989 through 2005 (n = 10,014). Logistic regression models were employed to generate adjusted odd ratios and their 95% confidence intervals. Male babies served as the referent category.

RESULTS

The sex ratio at birth was 1.18. The overall prevalence of stillbirth, neonatal mortality, and perinatal mortality was 7.2%, 4.5%, and 11.8%, respectively. Placental abruption was less likely to occur in mothers carrying female pregnancies than mothers of male infants (adjusted odds ratio [95% confidence interval] = 0.89 [0.86-0.93]). There were no significant sex differences with regards to stillbirth, neonatal mortality, and perinatal mortality. Similar findings were observed for preterm and term infants.

CONCLUSIONS

Although a preponderance of male infants was discernable among mothers with placental abruption, no sex difference in fetal survival was observed among the offspring of the mothers affected by placental abruption.

Examination of genetic polymorphisms in newborns for signatures of sex-specific prenatal selection

Success rate in human pregnancies is believed to be very low and sex-specific mechanisms may operate in prenatal loss. Assuming a sex-differential in prenatal loss exists, we examined genetic markers in biologically plausible targets in the HLA complex, other immune system-related and iron-regulatory genes in 388 healthy newborns from Wales (UK) using one sex as a control group for the other. Genotyping of 333 single nucleotide polymorphisms (SNPs) from 107 genes was achieved mainly by TaqMan assays. Twenty-two of autosomal SNPs showed frequency differences between 187 male and 201 female newborns either individually or as part of a haplotype. Of these, six markers (RXRB rs2076310, HLA complex haplotype HLA-DQA1 rs1142316-HLA-DRA rs7192-HSPA1B rs1061581, HIST1H1T rs198844, IFNG rs2069727, NKG2D rs10772266 and IRF4 heterozygosity) showed statistically robust differences between male and female newborns and multivariable modeling confirmed their independence. There were fewer males homozygote for combined wildtype genotypes of LIF rs929271, TP53 rs1042522 and MDM2 rs2279744 compared with females [OR = 0.3, 95% confidence interval (CI) = 0.1-0.8; P < 0.01] although these SNPs did not show any association individually. It is unlikely that SNPs have clinical utility as single markers in any trait with complex etiology but polygenic predictive models remain a possibility. If their validity is confirmed in larger studies of different populations and functional mechanisms of these preliminary associations are elucidated, these markers from the HLA complex, NKG2D region and cytokines may cumulatively have sufficient predictive value for susceptibility to prenatal selection in each sex.

The sex ratio of singleton offspring in assisted-conception pregnancies

OBJECTIVE

To evaluate the effect of intracytoplasmic sperm injection (ICSI) and male factor infertility on the sex ratio in births from assisted reproductive technology.

DESIGN

Historic cohort study.

SETTING

Clinic-based data.

PATIENT(S)

The study population included 15,164 singleton live births in the Society for Assisted Reproductive Technology national database for 2005 from cycles using ejaculated sperm, categorized by the use of insemination or ICSI and the absence or presence of male factor infertility, and cleavage- versus blastocyst-stage embryo transfers (ETs).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The probability of a male infant with and without the use of ICSI and in the presence or absence of male factor infertility.

RESULT(S)

The sex ratio for all U.S. live births in 2005 was 52.5%, versus 48.9% for cleavage-stage and 51.6% for blastocyst-stage embryos. With blastocyst-stage embryos, the sex ratios were 49.6% and 54.9% with and without ICSI and 52.6% and 50.0% with and without male factor infertility, respectively. With cleavage-stage embryos, the sex ratio was not significantly affected by ICSI or male factor infertility, singly or in combination.

CONCLUSION(S)

The use of ICSI, particularly with blastocyst-stage embryos, is associated with a decrease in the sex ratio of male infants.

Does fetal sex affect pregnancy outcome?

BACKGROUND

In maternal fetal medicine, gender differences in outcome are often observed.

OBJECTIVE

This article reviews the fetal sex-dependent differences found in many aspects of pregnancy, from conception through birth.

METHODS

The MEDLINE, EMBASE, and Current Contents databases were searched, for the years 1985 to 2006, using the following Medical Subject Headings and text words: fetal gender, finale, female, sex ratio at birth, pregnancy outcome, preterm birth, and stillbirth. The search was not limited by language. In addition, the bibliographies of known relevant articles were examined to capture any reports not already identified in the electronic search. All reports that provided information on gender differences in pregnancy outcome were included for review.

RESULTS

An extremely high male-to-female ratio was found in fetuses born after very short-duration pregnancy; this level declined around the 20th week and stabilized at term. In the absence of manipulation, both the sex ratio at birth and the population sex ratio have been found to remain consistent. A higher incidence of preterm birth and premature preterm rupture of membranes has been observed in different populations among mothers of male newborns compared with mothers of females. It has been speculated that this higher incidence may be linked to the relatively greater weight at lower gestational age of male newborns versus females. Women carrying male fetuses had higher rates of gestational diabetes mellitus, fetal macrosomia, failure to progress during the first and second stages of labor, cord prolapse, nuchal cord, and true umbilical cord knots. Cesarean sections were also more frequently found among male neonates compared with females.

CONCLUSIONS

Male sex is an independent risk factor for adverse pregnancy outcome. Evidence suggests that females have an advantage over males, with a better outcome in the perinatal period, particularly after preterm birth.