Effects of Promoting Long-term, Exclusive Breastfeeding on Adolescent Adiposity, Blood Pressure, and Growth Trajectories: A Secondary Analysis of a Randomized Clinical Trial

Importance Evidence that breastfeeding reduces child obesity risk and lowers blood pressure (BP) is based on potentially confounded observational studies. Objective To investigate the effects of a breastfeeding promotion intervention on adiposity and BP at age 16 years and on longitudinal growth trajectories from birth. Design, Setting, and Participants Cluster-randomized Promotion of Breastfeeding Intervention Trial. Belarusian maternity hospitals and affiliated polyclinics (the clusters) were allocated into intervention (n = 16) or control arms (n = 15) in 1996 and 1997. The trial participants were 17 046 breastfeeding mother-infant pairs; of these, 13 557 children (79.5%) were followed up at 16 years of age between September 2012 and July 2015. Interventions Breastfeeding promotion, modeled on the Baby-Friendly Hospital Initiative. Main Outcomes and Measures Body mass index (BMI, calculated as weight in kilograms divided by height in meters squared); fat and fat-free mass indices and percentage of body fat from bioimpedance; waist circumference; overweight and obesity; height; BP; and longitudinal growth trajectories. The primary analysis was modified intention-to-treat (without imputation for losses to follow-up) accounting for within-clinic clustering. Results We examined 13 557 children at a median age of 16.2 years (48.5% were girls). The intervention substantially increased breastfeeding duration and exclusivity compared with the control arm (exclusively breastfed: 45% vs 6% at 3 months, respectively). Mean differences at 16 years between intervention and control groups were 0.21 (95% CI, 0.06-0.36) for BMI; 0.21 kg/m 2 (95% CI, −0.03 to 0.44) for fat mass index; 0.00 kg/m 2 (95% CI, −0.21 to 0.22) for fat-free mass index; 0.71% (95% CI, −0.32 to 1.74) for percentage body fat; −0.73 cm (−2.48 to 1.02) for waist circumference; 0.05 cm (95% CI, −0.85 to 0.94) for height; −0.54 mm Hg (95% CI, −2.40 to 1.31) for systolic BP; and 0.71 mm Hg (95% CI, −0.68 to 2.10) for diastolic BP. The odds ratio for overweight/obesity (BMI ≥85th percentile vs z score changes after 8.5 years. Conclusions and Relevance A randomized intervention that increased the duration and exclusivity of breastfeeding was not associated with lowered adolescent obesity risk or BP. On the contrary, the prevalence of overweight/obesity was higher in the intervention arm. All mothers initiated breastfeeding, so findings may not apply to comparisons of the effects of breastfeeding vs formula feeding. Trial Registration isrctn.org:ISRCTN37687716; and clinicaltrials.gov:NCT01561612.