AbstractObjectiveTo determine the associations between haemoconcentration at the end of pregnancy (third trimester and delivery) and neonatal behaviour in healthy pregnant women supplemented with moderate doses of Fe.DesignA prospective longitudinal study in which obstetric and clinical history, maternal toxic habits, maternal anxiety and Hb levels were recorded at the third trimester and delivery. Neonatal behaviour was assessed at 48–72 h of age using the Neonatal Behavioral Assessment Scale.SettingUnit of Obstetrics and Gynaecology of the Sant Joan University Hospital in Reus, Tarragona (Spain).SubjectsA total of 210 healthy and well-nourished pregnant women and their full-term, normal-weight newborns.ResultsThe results showed that, after adjusting for confounders, in the third trimester the risk of haemoconcentration (6·2 % of pregnant women) was related to decreased neonatal state regulation (B=−1·273, P=0·006) and alertness (B=−1·848, P=0·006) scores. In addition, the risk of haemoconcentration at delivery (12·0 % of pregnant women) was also related to decreased neonatal state regulation (B=−0·796, P=0·021) and poor robustness and endurance (B=−0·921, P=0·005) scores.ConclusionsOur results show that the risk of haemoconcentration at the end of pregnancy is related to the neonate’s neurodevelopment (and self-regulation capabilities), suggesting that Fe supplementation patterns and maternal Fe status during pregnancy are important factors for neurodevelopment which may be carefully controlled.