Infant Feeding Practices and Maternal Sleep Outcomes in Early Postpartum

Background: Postpartum sleep disturbance is nearly universal, yet little is known about how infant feeding strategies influence the quantity or quality of sleep in the early postpartum period. Our objective was to examine whether supplementing with formula—often introduced to support shared caregiving or maternal rest—was associated with improved sleep quality or quantity in the early postpartum period. Study Design and Methods: The Postpartum Study (PPS) enrolled 317 pregnant individuals in their third trimester who completed telephone surveys on infant feeding practices and maternal sleep at one week, six weeks, and three months postpartum. Feeding was categorized as exclusive formula feeding versus breastmilk feeding (with or without formula supplementation). Additionally, participants were categorized by whether breastmilk was delivered directly at the breast exclusively or via bottle (exclusively or to supplement direct breastfeeding). Both variables were coded as binary indicators, with exclusive formula feeding and bottle feeding as reference groups. Sleep quality was measured using the Pittsburgh Sleep Quality Index (coded as good/very good vs. not good/poor), and nightly sleep hours were self-reported. Associations at each wave were estimated using logistic regression for sleep quality and linear regression for sleep quantity. Models were run unadjusted and adjusted for maternal age, race/ethnicity, parity, hypertensive disorders of pregnancy (yes/no), partnered status, and education. A secondary complete-case analysis was conducted among participants with data at all three time points. All analyses were conducted in R v4.3.1; two-sided p < 0.05 denoted statistical significance. Missing covariate data were