Association between preconception maternal stress and offspring birth weight: findings from an Australian longitudinal data linkage study

Objective Examine the relationship between preconception stress and offspring birth weight. Setting Population-based cohort study linked with state-based administrative perinatal data. Participants 6100 births from 3622 women from the 1973-1978 cohort of the Australian Longitudinal Study of Women's Health who (1) recorded a singleton birth between January 1997 and December 2011; (2) returned at least one follow-up survey within 3 years of conception; and (3) had complete data on perceived stress prior to conception. Primary outcome measures Linear generalised estimating equations were used to examine the relationship between preconception stress and a continuous measure of birth weight, exploring differences based on birth order and stress chronicity. The minimal sufficient adjustment set of covariates was determined by a directed acyclic graph. Results For all births, there was no relationship between moderate/high acute or chronic stress and offspring birth weight in grams. Among first births only, there was a trend towards a relationship between moderate/high chronic stress and offspring birth weight. Offspring sex was associated with birth weight in all models, with female babies born lighter than male babies on average, after adjusting for covariates (p<0.0001). Conclusions Effects of preconception stress on birth weight was largely driven by time to conception. With the timing of stress critical to its impact on obstetrical outcomes, preconception care should involve not only reproductive life planning but the space to provide interventions at critical periods so that optimal outcomes are achieved.