Fetal sex dependency of maternal vascular adaptation to pregnancy: a prospective population-based cohort study

Objective To investigate fetal sex dependency of maternal vascular adaptation to pregnancy as assessed by uteroplacental vascular resistance and maternal blood pressure. Design Prospective population-based cohort study. Setting Rotterdam, the Netherlands. Population In total, 8224 liveborn singleton pregnancies were included. Methods Maternal vascular adaptation was assessed in all trimesters of pregnancy. Pregnancies were stratified into being either complicated by the placental syndrome (i.e. pre-eclampsia, fetal growth restriction or preterm birth, n = 1229) or uncomplicated (n = 6995). Main outcome measures First trimester: blood pressures. Second trimester: blood pressures, pulsatility index of the uterine artery (PI-UtA). Third trimester: blood pressures, PI-UtA, presence of notching in the uterine artery. Results In women carrying a male fetus PI-UtA was higher than in women with a female fetus in the total group (second trimester P < 0.001, third trimester P = 0.005). Effect estimates differed between women with or without the placental syndrome. In the total group, women with a male fetus more often showed notching in the Doppler resistance pattern (odds ratio 1.42, 95% confidence interval 1.17-1.72). Different blood pressure patterns were observed between pregnant women with a male fetus and pregnant women with a female fetus and between complicated pregnancies and uncomplicated pregnancies. Conclusion Fetal sex is significantly associated with maternal vascular adaptation to pregnancy with differential effects in uncomplicated pregnancies and in pregnancies complicated by the placental syndrome.