Timing sensitivity of prenatal cortisol exposure and neurocognitive development.

Prenatal glucocorticoid exposure has been negatively associated with infant neurocognitive outcomes. However, questions about developmental timing effects across gestation remain. Participants were 253 mother-child dyads who participated in a prospective cohort study recruited in the first trimester of pregnancy. Diurnal cortisol was measured in maternal saliva samples collected across a single day within each trimester of pregnancy. Children (49.8% female) completed the Bayley Mental Development Scales, Third Edition at 6, 12, and 24 months and completed three observational executive function tasks at 24 months. Structural equation models adjusting for sociodemographic covariates were used to test study hypotheses. There was significant evidence for timing sensitivity. First-trimester diurnal cortisol (area under the curve) was negatively associated with cognitive and language development at 12 months and poorer inhibition at 24 months. Second-trimester cortisol exposure was negatively associated with language scores at 24 months. Third-trimester cortisol positively predicted performance in shifting between task rules (set shifting) at 24 months. Associations were not reliably moderated by child sex. Findings suggest that neurocognitive development is sensitive to prenatal glucocorticoid exposure as early as the first trimester and underscore the importance of assessing developmental timing in research on prenatal exposures for child health outcomes.