Impact of fetal gender on the incidence of preeclampsia

Preeclampsia is associated with significant maternal and fetal morbidity and mortality, with established risk factors. Fetal gender has been proposed as a potential independent risk factor for preeclampsia, though its exact role is not yet determined as studies to date have reported conflicting results. This study aimed to investigate the association between fetal gender and preeclampsia while accounting for key confounders. This retrospective cohort study was conducted at the Third Department of Obstetrics and Gynecology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Greece, between December 2018 and March 2025. Data extracted from electronic medical records encompassed maternal demographics, obstetric history, pre-pregnancy weight and body mass index (BMI), use of assisted reproductive technologies (ART), smoking status, parity, aspirin usage and uterine artery Doppler findings (z-score and bilateral uterine artery notching). Preeclampsia was diagnosed according to standard clinical criteria, and fetal gender was determined during routine second-trimester ultrasound and confirmed at delivery. Multivariable logistic regression was used to assess the association between potential risk factors and preeclampsia, adjusting for potential confounders. Interaction analyses were performed to examine potential effect modification between fetal gender and maternal age>35 years, BMI>25 kg/m², smoking, and uterine artery Doppler indices. A total of 9,603 singleton pregnancies were included; 68 women developed preeclampsia. Fetal gender was not associated with preeclampsia. Significant predictors included ART, higher pre-pregnancy BMI, elevated uterine artery z-score, and bilateral uterine artery notching. Maternal age, smoking, parity, and aspirin use were not significantly associated with preeclampsia. Interaction analyses revealed no statistically significant effect modification between male fetal gender and maternal age>35 years, BMI>25 kg/m², smoking, elevated uterine artery z-score, or bilateral uterine artery notching. Similarly, no significant interactions were observed between aspirin use and maternal risk factors or Doppler findings. Analysis by BMI category also showed no statistically significant interactions in any subgroup. Fetal gender was not associated with increased risk of preeclampsia and did not modify maternal or uteroplacental factors. Pre-pregnancy maternal BMI, use of ART and abnormal uterine artery Doppler findings were confirmed as key predictors of preeclampsia.