Maternal cortisol levels during pregnancy: Associations with fetal anthropometry and infant cognitive development at three months postpartum

Pregnancy involves profound endocrine and metabolic adaptations, such as the increase in maternal cortisol levels, which plays a central role in fetal maturation and appropriate fetal development. However, at high levels, evidence suggests that exposure to maternal cortisol can be harmful to fetal growth and subsequent infant neurodevelopment. This study examined the associations between maternal serum cortisol levels during gestation and fetal anthropometry, assessed by ultrasonography, both measured simultaneously in either the second or the third trimester of pregnancy. It also explored potential relationships between gestational cortisol and infant cognitive development at three months of age, evaluated using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III). This study is nested within a larger project involving mother-child dyads from southern Brazil. The data presented here refers to 632 dyads with complete fetal anthropometric measurements, serum cortisol data, and last menstrual period information. Among the 632 included dyads, 520 infants were assessed for cognitive development at three months of age. In adjusted analyses, higher gestational cortisol levels remained significantly and positively associated with fetal head circumference (B = 0.12, 95% CI: 0.05; 0.19, p = 0.001), abdominal circumference (B = 0.09, 95% CI: 0.02; 0.16, p = 0.015), femur length (B = 0.02, 95% CI: 0.00; 0.04, p = 0.013), and biparietal diameter (B = 0.03, 95% CI: 0.01; 0.05, p = 0.005). No significant association was observed for estimated fetal weight. Additionally, higher maternal cortisol levels during pregnancy were significantly associated with lower infant cognitive scores at three months (B = -0.05, 95% CI: -0.09; -0.01, p = 0.038). These findings suggest that gestational cortisol may exert distinct influences on fetal growth and early cognitive functioning, highlighting the importance of understanding its underlying biological mechanisms.