Randomized, placebo-controlled, calcium supplementation study in pregnant Gambian women: effects on breast-milk calcium concentrations and infant birth weight, growth, and bone mineral accretion in the first year of life.

Randomized, double-blind, placebo-controlled trial in pregnant women in rural The Gambia with uncomplicated singleton pregnancies and very low habitual calcium intake. Mothers and infants were followed through the first year of life to assess breast-milk composition, infant growth, and bone mineral outcomes.

Pregnant women received 1500 mg/day elemental calcium as calcium carbonate, given as 3 chewable tablets containing 500 mg elemental calcium each. Dosing was oral once daily from pregnancy week 20 until delivery; the comparator was placebo.

Calcium supplementation during the second half of pregnancy did not improve breast-milk calcium, infant birth weight, growth, or bone mineral status. Breast-milk calcium concentrations were similar between groups at L02, L13, and L52, and there was no significant effect on calcium, phosphorus, or the calcium-to-phosphorus ratio at any timepoint or on change over time. Infant birth weight was also similar (3.01 Ȁ 0.37 kg in the supplemented group vs 2.98 Ȁ 0.36 kg in placebo), and DXA outcomes at 13 and 52 weeks were generally similar between groups. There was a signal of slower increase in whole-body bone mineral content and bone area over time in supplemented infants, and a season-by-intervention interaction was seen for breast-milk phosphorus (P 0.006).

The trial was conducted in a single rural Gambian population with very low baseline calcium intake, which may limit generalizability. No meaningful between-group benefits were detected, and the observed signal toward slower bone mineral accretion raises concern but should be interpreted cautiously because the study appears to have limited power for subgroup or time-varying effects. Seasonal effects also complicated interpretation of breast-milk phosphorus results.