Background During pregnancy, negative emotions such as anxiety and depression may induce cortisol disruption. Cortisol can be transmitted to the fetus through the placental barrier, thereby affecting the neurodevelopment of the offspring.

Objective To investigate the relationship between placental cortisol, maternal depression during pregnancy, and neurodevelopment of 3-month-old infants.

Methods From September 2022 to September 2023, 171 pregnant women ordered routine prenatal checks at the obstetrics outpatient department of a tertiary hospital in Ningxia were selected using a prospective cohort design. After providing informed consent, these women participated in a questionnaire survey that covered general individual characteristics, prenatal depression, and sleep quality. At birth, placental samples were collected to measure cortisol levels using ELISA kits. Follow-up assessments on the neurodevelopmental of 3-month-old infants were conducted using the Warning Sign for Children Mental and Behavioral Development. LASSO regression analysis was conducted to screen the influencing factors of depression during pregnancy. Huber regression analysis was then applied to assess potential linear relationship between depression during pregnancy and placental cortisol levels. Log-binomial regression was used to analyze the linear relationships between cortisol levels and neurodevelopmental delay in 3-month-old infants. Additionally, a mediation effect model was fitted using R 4.3.3 to assess possible mediating role of cortisol in the association between prenatal depression and neurodevelopmental delay in 3-month-old infants.

Results The positive rate of prenatal depression was 33.33%. Nine factors affecting prenatal depression were identified by LASSO regression, including rural residence, high school education or above, extroverted personality characteristics, moderate early pregnancy reactions, baby sex expectation, prenatal anxiety, family dysfunction, exposure to stressful life events during pregnancy, and moderate prenatal sleep quality. The Huber regression model showed a positive linear correlation between prenatal depression and placental cortisol (P<0.05). With or without controlling confounding factors, the results of log-binomial regression modeling showed that cortisol levels were associated with a reduced risk of neurodevelopmental delay in 3-month-old infants (crude model: RR=0.988, 95%CI: 0.9768, 0.9996, P＜0.05; adjusted model: RR=0.988, 95%CI: 0.9764, 0.9993, P＜0.05). A mediating effect of placental cortisol between prenatal depression and the risk of neurodevelopmental delay in 3-month-old offspring was found statistically significant (P=0.045), accounting for 67.0% of the total effect.

Conclusion Prenatal depression is associated with elevated placental cortisol levels, and higher cortisol levels are found to be related to a lower risk of neurodevelopmental delay in infants. Placental cortisol mediates the relationship between prenatal depression and infant neurodevelopment.