Maternal and neonatal outcomes of vitamin D supplementation in hypovitaminosis D pregnancy: preg-D randomized trial

CONTEXT: Hypovitaminosis D during pregnancy is common and may have adverse maternal and neonatal effects. While randomized trials show that supplementation improves biochemical vitamin D status, the optimal dose and its effects on neonatal bone outcomes remain uncertain. OBJECTIVE: To compare the effects of 2 vitamin D supplementation doses during pregnancy on maternal and neonatal serum 25-hydroxyvitamin D (25(OH)D) at delivery, and on neonatal bone mineral content. METHODS: In this double-blind trial, pregnant women ≤17.5 weeks' gestation with baseline 25(OH)D 10 to 30 ng/mL were randomized to receive either 20 000 IU/week or 10 000 IU every 2 weeks (equivalent to 714 IU/day) vitamin D3. Primary outcomes were the proportion of women achieving a 25(OH)D level ≥20 ng/mL at delivery and neonatal bone mineral content (BMC) at ∼1 month of age. We used liquid chromatography tandem mass spectrometry (standard LC-MS/MS) at a CDC-certified laboratory. RESULTS: One hundred and ninety-two maternal neonatal pairs had complete biochemical data and 67 neonates had evaluable DXA scans. A significantly higher proportion (100%) of women and neonates (77%) in the higher dose group achieved 25(OH)D levels ≥20 ng/mL at delivery, compared with the lower dose group (85% and 40%, respectively, P = .001). Mean 25(OH)D in mothers and neonates at delivery followed a similar pattern (P = .001). However, neonatal subtotal whole-body BMC did not differ between groups (45.9 ± 8.5 vs 42.2 ± 7.1 g, respectively; P = .059), nor did neonatal bone mineral density or bone area. We did not identify any safety concerns related to supplementation. CONCLUSION: Higher dose vitamin D supplementation safely achieved biochemical sufficiency in mothers and neonates without measurable effect on neonatal bone outcomes.