INSIGHT Study Maternal Return to Work and Infant Weight Outcomes

Objective: Maternal return to work within 12 weeks of delivery is associated with poor child health and development. However, little is known about the impact of return to work on the risk of child obesity. We examined whether timing of maternal return to work is associated with rapid infant weight gain from 0 to 6 months and weight-for-length at 1 year. Methods: Secondary data analysis of 279 mother-newborn dyads from the Intervention Nurses Start Infants Growing on Healthy Trajectories Study, a randomized controlled trial evaluating a responsive parenting (RP) intervention. Rapid infant weight gain from 0 to 6 months was assessed using conditional weight gain (CWG) scores. Infant weight-for-length was calculated using World Health Organization reference values. Analysis of variance (ANOVA) examined whether infant weight outcomes differed by timing of maternal return to work (≤12 weeks vs >12 weeks after delivery). Moderation by study group (RP intervention vs safety control) and mediation by breastmilk feeding were examined in ANOVA models. Results: Among 261 mothers, approximately one half (n = 130) returned to work within 12 weeks. Compared with infants of mothers who returned to work after 12 weeks, infants of mothers who returned to work within 12 weeks had greater CWG scores from 0 to 6 months (P = .006) and were heavier at 1 year (P = .05). These associations were not moderated by study group or mediated by breastmilk feeding. Conclusions: Maternal return to work within 12 weeks was associated with rapid infant weight gain in the first 6 months and greater weight-for-length at 1 year, although the mechanisms to explain our findings are unclear.