Abstract

Abstract Environmental influences before and during pregnancy significantly impact offspring development. This study investigates open research questions regarding the associations between maternal early life stress (ELS), prenatal psychosocial stress, prenatal hair cortisol (HC), and birth outcomes in Argentinian women. Data on ELS, prenatal life events, HC (two samples representing first and second half of pregnancy), and birth outcomes were collected from middle‐class Argentinian women ( N = 69) upon delivery. Linear mixed models indicated that HC increased from the first half to the second half of pregnancy with considerable variability in the starting values and slopes between individuals. Mothers who experienced more ELS, were taller, or more educated, tended to show lower increases in HC. Older age was positively related to HC increases. Our data did not suggest an interaction between ELS and prenatal life events in relation to HC. We found that the change in HC was most likely negatively associated with birth weight. Our data are most compatible with either a weak or the absence of an association between ELS or prenatal life events and absolute values of HC. Mothers with stronger increases in hair cortisol tended to have newborns with slightly lower birth weight. Hence, ELS and birthweight may either have been related to changes in cortisol exposure during pregnancy or to factors that influence accumulation or retention of cortisol in hair.