The association between maternal prenatal hair cortisol concentration and preterm birth: A systematic review and meta-analysis

The risk of preterm birth (PTB) increases when experiencing stress during pregnancy. Chronic stress has been associated with a dysregulation of the hypothalamic-pituitary-adrenal axis, for which hair cortisol concentration (HCC) is a promising biomarker. However, previous studies on the association between HCC and PTB yielded inconsistent results. This systematic review and meta-analysis synthesized previous studies on the association between maternal HCC before and during pregnancy and spontaneous PTB. Data was extracted from N = 11 studies with k = 19 effect sizes retrieved from PubMed, Embase, Web of Science, CINAHL and citation searching by hand in June 2023 and updated in October 2023. Standardized mean differences were calculated, and a random-effects three-level meta-analysis was conducted. Effect heterogeneity was assessed using Q and I2. HCC during pregnancy was higher among PTB than term groups, but effects were not statistically significant (z = 0.11, 95% CI: − 0.28, 0.51, p = .54) and total heterogeneity was high (Q16 = 60.01, p