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. Tweetable abstract: Fetal sex is significantly associated with maternal vascular adaptation to pregnancy.