Abstract
BACKGROUND: Evidence suggests maternal birth experience impacts infant health. Alterations of the infant's hypothalamus-pituitary-adrenal (HPA) axis are discussed as one possible underlying mechanism. This study aimed to investigate both objective and subjective birth experience as potential predictors of offspring's hair glucocorticoid concentrations (GCs) and infant development, respectively. Further, we examined the role of hair GCs for prospective infant development in different domains. METHODS: n = 263 mothers participating in the prospective cohort study DREAM(HAIR) completed questionnaires about their objective and subjective birth experience approximately eight weeks after birth. Additionally, hair samples from n = 286 infants were taken around ten days (neonatal hair GCs) and eight weeks after birth (infant hair GCs) and long-term integrated hair cortisol and cortisone levels were measured in scalp-near 2-cm segments. Infant development (communication, gross motor, fine motor, problem-solving, personal-social) was assessed 14 months after birth using the Ages and Stages Questionnaire - 3 (ASQ-3). RESULTS: No significant associations were found between objective or subjective birth experience and most domains of infant development, except that a more negative objective birth experience predicted poorer fine motor skills. Additionally, a more negative objective birth experience was linked to lower infant hair cortisone levels and a higher cortisol/cortisone ratio, while a more negative subjective experience was associated with higher neonatal hair cortisol. Lower neonatal hair cortisone showed a link to poorer personal-social development. However, after correction for multiple testing, only the associations between a more negative objective birth experience and lower hair cortisone and a higher cortisol/cortisone ratio at eight weeks remained significant. CONCLUSIONS: Objective aspects of the birth experience may have a more enduring impact on infant hair GCs than maternal subjective perceptions, particularly with higher birth complications being linked to lower infant cortisone and a higher infant cortisol/cortisone ratio. Given that this ratio may indicate reduced enzymatic activity in converting cortisol to its inactive form, results suggest that birth complications could affect the infant's glucocorticoid metabolism. No robust associations were found between birth experiences or hair GCs and infant development. Further research in more diverse, at-risk populations is needed to clarify these complex relationships.