Maternal Lifetime Trauma and Birthweight: Effect Modification by In Utero Cortisol and Child Sex.

OBJECTIVES: To evaluate associations between maternal lifetime traumatic stress and offspring birthweight and examine modifying effects of third trimester cortisol and fetal sex.

STUDY DESIGN: Analyses included 314 mother-infant dyads from an ethnically mixed pregnancy cohort. Maternal lifetime trauma was reported via the Life Stressor Checklist-Revised. Fenton birthweight for gestational age z-scores (BWGA-z) were calculated. A 3-cm scalp-nearest maternal hair segment collected at birth was assayed to reflect cumulative third trimester cortisol secretion. Multivariable regression was used to investigate associations between maternal lifetime trauma and BWGA-z and examine 2- and 3-way interactions with cortisol and fetal sex. Because subjects with low or high cortisol levels could represent susceptible populations, varying coefficient models that relax the linearity assumption on cortisol level were used to assess the modification of maternal lifetime trauma associations with BWGA-z as a function of cortisol.

RESULTS: Women were primarily minorities (41% Hispanic, 26% black) with ≤12 years education (63%); 63% reported ≥1 traumatic event. Prenatal cortisol modified the association between maternal lifetime trauma and birthweight. Women with higher lifetime trauma and increased cortisol had significantly lower birthweight infants in males; among males exposed to the 90th percentile of cortisol, a 1-unit increase in trauma score was associated with a 0.19-unit decrease in BWGA-z (95% CI, -0.34 to -0.04). Associations among females were nonsignificant, regardless of cortisol level.

CONCLUSIONS: These findings underscore the need to consider complex interactions among maternal trauma, disrupted in utero cortisol production, and fetal sex to fully elucidate intergenerational effects of maternal lifetime trauma.