BACKGROUND: In-hospital formula feeding (IHFF) of breastfed infants is associated with shorter duration of breastfeeding. Despite evidence-based guidelines on when IHFF is appropriate, many infants are given formula unnecessarily during the postpartum hospital stay. To account for selection bias inherent in observational data, in this study, we estimate liberal and conservative bounds for the association between hospital formula feeding and duration of breastfeeding.
METHODS: Infants enrolled in the Minnesota Special Supplemental Nutrition Program for Women, Infants, and Children were selected. Breastfed infants given formula were matched with infants exclusively breastfed (n = 5310) by using propensity scoring methods to adjust for potential confounders. Cox regression of the matched sample was stratified on feeding status. A second, more conservative analysis (n = 4836) was adjusted for medical indications for supplementation.
RESULTS: Hazard ratios (HR) for weaning increased across time. In the first analysis, the HR across the first year was 6.1 (95% confidence interval [CI] 4.9–7.5), with HRs increasing with age (first month: HR = 4.1 [95% CI 3.5–4.7]; 1–6 months: HR = 8.2 [95% CI 5.6–12.1]; >6 months: HR = 14.6 [95% CI 8.9–24.0]). The second, more conservative analysis revealed that infants exposed to IHFF had 2.5 times the hazard of weaning compared with infants who were exclusively breastfed (HR = 2.5; 95% CI 1.9–3.4).
CONCLUSIONS: IHFF was associated with earlier weaning, with infants exposed to IHFF at 2.5 to 6 times higher risk in the first year than infants exclusively breastfed. Strategies to reduce IHFF include prenatal education, peer counseling, hospital staff and physician education, and skin-to-skin contact.