Parity‐related variation in cortisol concentrations in hair during pregnancy

OBJECTIVE: To investigate hair cortisol concentrations (HCC) monthly in pregnant women and to explore the effect of parity. DESIGN: Prospective cohort study from gestational week (GW) 26, at childbirth and postpartum. SETTING: An antenatal care clinic in southeast Sweden. SAMPLE: 390 pregnant women. METHODS: Cortisol was measured using radioimmunoassay in methanol extracts of ground hair samples. MAIN OUTCOME MEASURES: Hair cortisol concentrations. RESULTS: Both primi‐ and multiparae exhibited an increase in HCC throughout pregnancy. Primiparae had significantly higher HCC in the latter part of the last trimester compared with multiparae (1 month P = 0.003, 2 months P = 0.038). The use of psychotropic medication in the first trimester correlated to HCC postpartum (P < 0.001). HCC in GW 14–17 was associated with HCC in GW 18–21 (primiparae and multiparae, P < 0.001), GW 22–25 (primiparae P = 0.036, multiparae P = 0.033), and 2 months postpartum (primiparae P = 0.049). HCC in GW 18–21 was associated with GW 22–25 in both primiparae (P < 0.001) and multiparae (P < 0.001) as well as 2 months prior to childbirth among primiparae (<0.037). In general, all estimates of HCC in pregnancy and postpartum showed a significant association between HCC for a specific month and the HCC in the previous month (all P < 0.001), except for the association of HCC among primiparae in GW 22–25 and 3 months prior to childbirth. CONCLUSIONS: Increased cortisol concentrations in hair were observed during pregnancy, which decreased 3 months prior to childbirth in multiparae. The results indicate a quicker suppression of the hypothalamic CRH (corticotropin‐releasing hormone) production by placenta CRH in multiparous women. TWEETABLE ABSTRACT: Multiparae have a quicker suppression of hypothalamic CRH production by placenta CRH during pregnancy compared to primiparae.