Randomized, placebo-controlled, calcium supplementation trial in pregnant Gambian women accustomed to a low calcium intake: effects on maternal blood pressure and infant growth

Randomized, double-blind, placebo-controlled trial in pregnant women in rural West Kiang, The Gambia, with very low habitual calcium intake and uncomplicated singleton pregnancies. The active calcium arm included women enrolled at 18-22 weeks' gestation, with analyses reported on 260 women in the final calcium analytic set.

Pregnant women in the active arm received 1500 mg elemental calcium per day as 3 oral chewable calcium carbonate tablets (500 mg each) from about 18 to 22 weeks' gestation until delivery, with tablets taken daily in the evening; during Ramadan they were taken after fasting ended and before the main meal. Mean supplementation duration was 20.5 6 3.0 weeks and reported compliance was 97 6 6%.

Calcium supplementation did not lower maternal blood pressure or improve infant growth. In the calcium group, the P20 to P36 change in blood pressure was not meaningfully different from placebo for systolic blood pressure, 20.64 6 0.65% (P = 0.3), or diastolic blood pressure, 20.22 6 1.15% (P = 0.8). Infant outcomes were also unchanged, with birth weight 2.9 6 0.4 kg (n = 171), birth length 485 6 24 mm (n = 171), and 52-week weight 7.9 6 1.1 kg (n = 243). The authors concluded that the lack of benefit may reflect adaptation to chronically low calcium intake and other lifestyle factors despite high adherence.

Substantial post-randomization loss reduced the calcium arm from 330 randomized women to 260 in the final analytic set, and infant measurements were available for smaller subsets. The trial was conducted in a single rural Gambian population with very low baseline calcium intake, which limits generalizability. Some outcomes were missing by time point, and the absence of effect may be specific to this setting and supplementation window.