Background: : Pre-eclampsia (PE) is a major pregnancy disorder complicating up to 8% of pregnancies. Increasing evidence indicates a sex-specific interplay between the mother, placenta and fetus. This may lead to different adaptive mechanisms during pregnancy.

Methods: We performed an individual participant data meta-analysis to determine associations of fetal sex and PE, with specific focus on gestational age at delivery in PE. This was done on 219 575 independent live-born singleton pregnancies, with a gestational age at birth between 22.0 and 43.0 weeks of gestation, from 11 studies participating in a worldwide consortium of international research groups focusing on pregnancy.

Results: Of the women, 9033 (4.1%) experienced PE in their pregnancy and 48.8% of the fetuses were female versus 51.2% male. No differences in the female/male distribution were observed with respect to term PE (delivered ≥ 37 weeks). Preterm PE (delivered < 37 weeks) was slightly more prevalent among pregnancies with a female fetus than in pregnancies with a male fetus [odds ratio (OR) 1.11, 95% confidence interval (CI) 1.02-1.21]. Very preterm PE (delivered < 34 weeks) was even more prevalent among pregnancies with a female fetus as compared with pregnancies with a male fetus (OR 1.36, 95% CI 1.17-1.59).

Conclusions: Sexual dimorphic differences in the occurrence of PE exist, with preterm PE being more prevalent among pregnancies with a female fetus as compared with pregnancies with a male fetus and with no differences with respect to term PE.