Differences in pregnancy complications and outcomes by fetal gender among Japanese women: a multicenter cross-sectional study

Abstract

Abstract The association between fetal gender and rare pregnancy complications has not been extensively investigated, and no studies have examined this association in Japanese women. Thus, we used a large Japanese birth registry database to investigate the extent to which fetal gender affects various pregnancy outcomes. We analyzed 1,098,268 women with a singleton delivery with no congenital anomaly at 22 weeks or later between 2007 and 2015. Women carrying a male fetus had a significantly higher risk of placental abruption (adjusted risk ratio [aRR] 1.15, 95% confidence interval (CI) 1.10–1.20)], preterm delivery (aRR 1.20, 95% CI 1.19–1.22), instrumental delivery (aRR 1.27, 95% CI 1.26–1.29), and cesarean delivery (aRR 1.01, 95% CI 1.00–1.02). In contrast, they had a significantly lower risk of preeclampsia (aRR 0.92, 95% CI 0.89–0.94), placenta accreta (aRR 0.90, 95% CI 0.85–0.96), atonic hemorrhage (aRR 0.95, 95% CI 0.93–0.96), and maternal blood transfusion (aRR 0.95, 95% CI 0.92–0.99). Our findings demonstrate a significant association between fetal gender and various pregnancy complications and delivery outcomes among Japanese women.