Maternal pregnancy-associated plasma protein A (PAPP-A) concentration was estimated in 272 pregnancies. Paired samples at 34 weeks of gestation and within 48 h before delivery were compared in relation to fetal and maternal blood group and fetal sex. The PAPP-A values were significantly higher both at 34 weeks and near delivery in rhesus-negative bearers. Mothers of male babies had higher PAPP-A values near delivery but not significantly higher at 34 weeks. This supports earlier findings that some placental hormones are higher in male bearers.