Role of body mass index and gestational weight gain in breastfeeding outcomes

Abstract

Objective: This study determined whether high maternal prepregnancy body mass index (BMI) and/or excess gestational weight gain (GWG) is associated with reduced breastfeeding duration and earlier formula supplementation.

Study design: A prospective longitudinal cohort of postpartum women (n=718), who were a subset of a larger randomized trial, was followed for 6 months postdelivery. We evaluated the relationship between BMI or BMI/GWG groups and timing of breastfeeding cessation and introduction of formula using Kaplan-Meier curves and log-rank tests. Then, we used multivariable Cox proportional hazards models to evaluate the relationship between BMI and BMI/GWG on these breastfeeding outcomes after controlling for potential confounding variables.

Results: The expected relationships between high BMI and high BMI/GWG and poor breastfeeding outcomes were observed in Kaplan-Meier curves. However, after adjusting for relevant maternal and infant covariates in the Cox models, the differences became nonsignificant. Prepregnancy BMI category was not statistically associated with breastfeeding duration (p=0.06) or timing of formula introduction (p=0.15). Similarly, BMI and GWG in combination were not associated with duration (p=0.33) or timing of formula introduction (p=0.18). Mothers' intended breastfeeding duration and rating of the importance of breastfeeding remained the only significant modifiable predictors of breastfeeding outcomes in the final models.

Conclusions: Maternal BMI and GWG were not significantly associated with breastfeeding outcomes after adjusting for confounding variables. Mothers' plans for breastfeeding duration and the importance mothers assign to breastfeeding remain the optimal intervention points for lengthening breastfeeding duration and reducing formula supplementation.

Trial registration: ClinicalTrials.gov NCT00360204.

FIG. 1.

Flow diagram for determination of final sample. IOM, Institute of Medicine.

FIG. 2.

Kaplan–Meier curves for breastfeeding duration stratified by (A) body mass index (BMI) or (B) BMI/gestational weight gain (GWG) group. BMI groups include Normal, Overweight, or Obese. BMI/adherence to Institute of Medicine GWG guideline groups include Normal/Recommended (NR), Overweight-Obese/Recommended (OOR), Normal/More (NM), Overweight/More (OWM), and Obese/More (OBM).

FIG. 3.

Kaplan–Meier curves for time to formula use stratified by (A) BMI or (B) BMI/GWG group. BMI groups include Normal, Overweight, or Obese. BMI/adherence to Institute of Medicine GWG guideline groups include Normal/Recommended (NR), Overweight-Obese/Recommended (OOR), Normal/More (NM), Overweight/More (OWM), and Obese/More (OBM).