The association between pre-pregnancy and first-trimester hair cortisol and preterm birth: a causal inference model

Adverse life events and chronic psychological distress before and during pregnancy have frequently been associated with preterm birth but the biological underpinnings remain unclear. We investigated the association between corticosteroid levels in pre-pregnancy and first-trimester hair and the risk of preterm birth. We followed N = 1,807 pregnant women from a prospective pre-birth cohort study in Lima, Perú. Hair samples were taken at the end of the first pregnancy trimester. The two most proximal 3 cm segments to the scalp (representing pre-pregnancy and first-trimester) were analyzed to obtain hair cortisol and cortisone concentrations (HCC and HCNC). Preterm birth was defined as birth