Effect of calcium plus vitamin D supplementation during pregnancy in Brazilian adolescent mothers: a randomized, placebo-controlled trial.

Randomized, placebo-controlled trial in Brazilian adolescent mothers aged 13-19 years with singleton first pregnancies, enrolled at 23-29 weeks' gestation and intending to exclusively or predominantly breastfeed. In the calcium plus vitamin D arm, 30 participants were randomized; allocation was 1:1 using permuted blocks of size 10.

Oral capsule containing calcium carbonate 600 mg/day plus cholecalciferol (vitamin D3) 200 IU/day, taken once daily with breakfast from 26 weeks of pregnancy until parturition. The regimen was compared with placebo in a randomized, placebo-controlled design.

Calcium plus vitamin D during late pregnancy was associated with better postpartum bone status, especially at the lumbar spine, and less femoral neck bone loss during early lactation. At 5 weeks postpartum, lumbar spine BMD was 1.098 ± 0.172 g/cm^2 vs 1.030 ± 0.114 g/cm^2, and lumbar spine BMD z-score was -0.69 ± 1.22 vs -1.30 ± 0.86 in the placebo group. The authors concluded that supplementation resulted in higher lumbar spine bone mass and a reduced rate of femoral neck bone loss during the first 20 weeks of lactation. No adverse events were reported.

Sample size was small, with only 30 participants in the active arm, limiting precision and generalizability. Follow-up was short, extending only to 20 weeks postpartum, so the durability of the bone effects remains uncertain. The population was narrow: Brazilian adolescent mothers with habitually low calcium intake, which may limit applicability to other pregnant populations.