Effects of high‐dose antenatal 3rd‐trimester vitamin D supplementation (35,000 IU/week) on maternal and newborn vitamin D status: a randomized placebo‐controlled trial in Dhaka, Bangladesh

Maternal‐infant vitamin D status in South Asia may be suboptimal. Yet, high dose prenatal vitamin D supplementation dose regimens have not been widely studied. In a double‐blinded randomized controlled trial in Dhaka, 160 pregnant women were assigned to vitamin D3 35,000 IU/week (VD) or placebo (P) from 26–29 weeks gestation to delivery. The primary biochemical efficacy outcome was serum 25‐hydroxyvitamin D concentration (25(OH)D) and the primary safety measure was maternal serum calcium. Mean maternal 25(OH)D was similar in the VD and P groups at baseline (45 vs. 44 nmol/L; P=0.66), but significantly differed at delivery (134 vs. 39 nmol/L, P<0.001; N=133). Women were more likely to attain >=50 nmol/L and >=80 nmol/L at delivery with VD (100% & 97%, respectively) vs. P (22% & 5%, respectively). Cord 25(OH)D was significantly higher with VD vs. P (103 vs. 39 nmol/L; P<0.001; N=132), and significantly more newborns had cord 25(OH)D>=50 nmol/L with VD vs. P (95% vs. 19%; P<0.001). VD did not cause documented maternal hypercalcemia or other supplement‐related serious adverse events. In conclusion, prenatal 3rd‐trimester supplementation with 35,000 IU vitamin D3/week prevented perinatal vitamin D insufficiency and was well tolerated. Further trials are needed to determine if increases in 25(OH)D due to high‐dose VD supplementation are safe and lead to maternal‐infant health benefits. Support: Thrasher Research Fund