Fetal gender distribution in post-term pregnancy and intrauterine death: Maternal and neonatal outcomes by fetal sex

Abstract

Aims:Fetal sex plays an important role in pregnancy and its outcomes due to hormonal and chromosomal differences. The current study examines the effect of fetal sex on delivery time, intrauterine death and maternal-neonatal outcomes.Methods:Pregnant women who gave birth in University of Health Sciences Turkey, Tepecik Training and Research Hospital Delivery Unit between 2014 and 2019 were screened retrospectively for the study. Pregnancies of ≥37 weeks (259 days) were included in the study, and pregnancies with ≥42 weeks (294 days) were classified as post-term (prolonged) pregnancy. Intrauterine death and maternal-neonatal outcomes were compared according to fetal gender.Results:The prevalence of post-term pregnancy was 0.76%. A total of 45,147 pregnancies were found, including 22,788 (50.5%) males (M) and 22,359 (49.5%) females (F) who met our criteria for the study. In births between 37-40 0/6 weeks male sexes ratio was higher (M/F sex ratio: 37 0/6 weeks: 1.05; 38 0/6 weeks: 1.01; 39 0/6 weeks: 1.01). The female sex birth rate becames more prominent after the 40th week, 75% of the newborns at the 44th week were observed to be female (M/F sex ratio: 44 0/6 weeks: 0.33). However, although female sex ratio was higher in post-term pregnancies, contrary to the literature, this difference was not significant. Intrauterine fetal death was observed more frequent in post-term pregnancies than term pregnancies (0.93% vs 0.3%, p=0.017). The risk of intrauterine fetal death was approximately three times higher in post-term pregnancies than term pregnancies (Odds ratio: 3.16; 95% confidence interval: 1.16-8.58). In post-term pregnancies, birth weight (3458.7±462.9 g vs. 3338.5±416.5 g), head circumference (35.2±1.1 cm vs. 34.9±1 cm) and body length [50 (44-56) cm vs. 50 (40-55) cm] were higher in male sexes and all these results were statistically significant (p=0.049, p=0.004 and p=0.003, respectively).Conclusions:Contrary to the literature, fetal sex is not a significant risk factor in post-term pregnancy. But intrauterine death increases about 3-fold in post-term fetuses compared to term fetuses.

Keywords

• post-term pregnancy
• prolonged pregnancy
• fetal sex
• birth time
• stillbirth
• pregnancy outcome