Association Between Gestational Weight Gain and Delayed Onset of Lactation: The Moderating Effects of Race/Ethnicity.

Background: In the United States, a high percentage of pregnant women gain weight outside of the current Institute of Medicine's (IOM) gestational weight gain (GWG) recommendations. There is limited research examining the relationship between GWG and onset of lactation. Delayed onset of lactation (DOL) can negatively affect breastfeeding outcomes.

Methods: Secondary data analysis was conducted using data from 2,053 women who participated in the population-based Infant Feeding Practices Study II between 2005 and 2007. The main outcome of interest was maternal perception of DOL, defined as milk coming in >3 days postpartum. Three categories of GWG were created based on the IOM's revised cutoff: inadequate, adequate, and excessive. Descriptive statistics and multivariable logistic regression modeling were performed. Interactions between GWG and race/ethnicity on DOL were examined to test whether the relationship between GWG and DOL differs by race/ethnicity.

Results: Overall, 23.7% of the study sample reported DOL. Of these, 49.5% and 19.5% of women had excessive GWG and inadequate GWG, respectively. After adjusting for potential confounders, there was a significant interaction between GWG and race/ethnicity on DOL. Among non-Hispanic white women, the odds of DOL were higher in women with excessive GWG compared to those who had the recommended GWG (OR 1.47, 95% CI 1.14-1.90, p = 0.003). For other race/ethnicity groups, no significant relationships between GWG and DOL were detected.

Conclusions: With the increasing rates of excessive GWG, it is critical to identify populations at increased risk of DOL and provide targeted breastfeeding support, especially in the early postpartum period.