Study outcomes and measurement
The primary outcomes of interest of the study are fat-mass index (FMI) and fat-free mass index (FFMI) (i.e., mass divided by squared height) in mothers and newborns. Secondary study outcomes are %FFM and %FM of total body weight in mothers and newborns; maternal BMI; and newborn length-for-age, weight-for-age, and weight-for-length z-scores. A sample size of 440 newborns per study arm (880 in total) was required to detect an effect size (Cohen’s d) of 0.2 on FFMI and 0.4 for an interaction effect between supplementation and maternal low versus high BMI (<21 versus ≥21 kg/mBody composition assessment of mothers and newborns was conducted within 3 weeks postpartum (mean ± SD days after delivery: 18.2 ± 3.96). Newborn weight was measured to the nearest 10 g using a Seca 384 scale, and length was measured to the nearest 1 mm using a Seca 416 length board. Maternal weight was measured to the nearest 100 g using a Seca 876 scale and height was measured to the nearest 1 mm using a ShorrBoard. All measurements were taken in duplicate and a third measurement was taken when there was a large discrepancy between the duplicate measurements. We used the average of the 2 closest anthropometric measurements for analysis. Anthropometric indices of length-for-age, weight-for-age, and weight-for-length 