Plain language summary
In Bangladesh, 30% of newborns are small for gestational age and 36% of children under 5-years of age have stunted growth. Some previous studies suggest that supplementing mums-to-be with vitamin D during and/or after pregnancy may improve foetal and infant growth. The aim of this trial was to evaluate the dose-dependent effects of vitamin D supplementation on infant growth in Bangladesh. Over 1,100 pregnant women were split into five groups. One group received no vitamin D (placebo group). Three groups received supplementation from mid pregnancy in doses of 4200 IU, 16,800 IU, and 28,000 IU per week. The fifth group received 28,000 IU vitamin D per week during pregnancy, as well as 28,000 IU weekly for 26 weeks after childbirth. At the start of the study, 64% of women were vitamin D deficient (defined as 25(OH)D<30 nmol/L). The vitamin D status of the women was similar across the groups. Among 1,164 infants assessed at 1 year of age, there were no significant differences across groups in the length-for-age scores. Other anthropometric measures, birth outcomes, and morbidity did not differ significantly across groups. The researchers concluded that maternal vitamin D supplementation from mid pregnancy until birth or until 6 months post-partum did not improve foetal or infant growth. The findings of the study do not support routine vitamin D supplementation in pregnancy or lactation to improve birth outcomes or infant growth, even in communities with endemic vitamin D deficiency and foetal-infant growth restriction.
Abstract
BACKGROUND It is unclear whether maternal vitamin D supplementation during pregnancy and lactation improves fetal and infant growth in regions where vitamin D deficiency is common. METHODS We conducted a randomized, double-blind, placebo-controlled trial in Bangladesh to assess the effects of weekly prenatal vitamin D supplementation (from 17 to 24 weeks of gestation until birth) and postpartum vitamin D supplementation on the primary outcome of infants' length-for-age z scores at 1 year according to World Health Organization (WHO) child growth standards. One group received neither prenatal nor postpartum vitamin D (placebo group). Three groups received prenatal supplementation only, in doses of 4200 IU (prenatal 4200 group), 16,800 IU (prenatal 16,800 group), and 28,000 IU (prenatal 28,000 group). The fifth group received prenatal supplementation as well as 26 weeks of postpartum supplementation in the amount of 28,000 IU (prenatal and postpartum 28,000 group). RESULTS Among 1164 infants assessed at 1 year of age (89.5% of 1300 pregnancies), there were no significant differences across groups in the mean (±SD) length-for-age z scores. Scores were as follows: placebo, -0.93±1.05; prenatal 4200, -1.11±1.12; prenatal 16,800, -0.97±0.97; prenatal 28,000, -1.06±1.07; and prenatal and postpartum 28,000, -0.94±1.00 (P=0.23 for a global test of differences across groups). Other anthropometric measures, birth outcomes, and morbidity did not differ significantly across groups. Vitamin D supplementation had expected effects on maternal and infant serum 25-hydroxyvitamin D and calcium concentrations, maternal urinary calcium excretion, and maternal parathyroid hormone concentrations. There were no significant differences in the frequencies of adverse events across groups, with the exception of a higher rate of possible hypercalciuria among the women receiving the highest dose. CONCLUSIONS In a population with widespread prenatal vitamin D deficiency and fetal and infant growth restriction, maternal vitamin D supplementation from midpregnancy until birth or until 6 months post partum did not improve fetal or infant growth. (Funded by the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT01924013 .).
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