Effects of vitamin A and β-carotene supplementation on birth size and length of gestation in rural Bangladesh: a cluster-randomized trial.

Cluster-randomized trial conducted in rural northwestern Bangladesh (Gaibandha and Rangpur districts) from 2001 to 2007. Pregnant women were enrolled in the first trimester and followed through 3 months postpartum; active intervention arm sizes were 5,897 for vitamin A and 6,012 for beta-carotene.

Pregnant women received a weekly oral capsule from enrollment in pregnancy until 3 months postpartum. The vitamin A arm received retinyl palmitate 23,300 IU (7000 mg REs) in soybean oil, and the beta-carotene arm received all-trans beta-carotene 42 mg (7000 mg REs by the 6:1 conversion ratio); the comparator was an identical-appearing placebo capsule.

Weekly prenatal vitamin A or beta-carotene supplementation did not improve birth size or gestational duration in this population. Birth weight was essentially unchanged for vitamin A versus placebo (2447 g vs 2447 g; difference 0.0, 95% CI -18 to 17; P = 0.97) and slightly lower with beta-carotene (2429 g vs 2447 g; difference -18, 95% CI -37 to 0; P = 0.06). Length, head circumference, chest circumference, midupper arm circumference, ponderal index, and gestational duration were also null: for vitamin A, length difference 0.04 cm (P = 0.43) and gestational duration difference -0.01 weeks (P = 0.83); for beta-carotene, length difference -0.03 cm (P = 0.62) and gestational duration difference 0.00 weeks (P = 0.96). The authors concluded that neither supplement reduced low birth weight, small-for-gestational-age, or preterm birth risk.

The trial was conducted in a single rural Bangladeshi setting, so generalizability is limited. The active-arm extract does not state allocation ratios, and the main findings were null despite large group sizes, leaving little evidence of clinically meaningful benefit. Some beta-carotene estimates were borderline but not statistically significant, which does not change the overall negative/null interpretation.