Safety and Effectiveness of High-Dose Vitamin D Supplementation From Early Pregnancy: A Randomized Controlled Trial With Implications for African American Women [ID 1651]

INTRODUCTION: Vitamin D sufficiency has been associated with fewer adverse pregnancy outcomes; therefore, we assessed the efficacy of higher-dose vitamin D supplementation (4,400 IU/day) in achieving the optimal maternal 25(OH)D concentration of greater than or equal to 100 nmol/L (40 ng/mL) and its potential to reduce adverse pregnancy outcomes, compared to standard-dose supplementation (400 IU/day). METHODS: This was a single-site, prospective, randomized trial involving 245 pregnant women at less than or equal to 14 weeks of gestation. Participants received either 400 IU (n=112) or 4,400 IU (n=133) of vitamin D daily until delivery. Circulating 25(OH)D concentrations were assessed monthly. A composite of perinatal morbidities, such as hypertensive disorders, preterm birth, and miscarriage, were compared by intention to treat group and by achievement of optimal 25(OH)D status. Data was analyzed using multiple logistic regression models in SAS 9.4 (Cary, NC). RESULTS: By the second month of supplementation, women in the treatment group had significantly higher 25(OH)D concentrations compared to the control group, and this difference was sustained through delivery ( P <.001). In the high-dose supplementation group, 86.5% of women achieved the optimal 25(OH)D concentration compared to 39.3% in the standard-dose group ( P <.0001). African American women in the high-dose group had a significant reduction in composite perinatal morbidity in the intention to treat analysis (odds ratio 0.26, P =.034). CONCLUSIONS/IMPLICATIONS: High-dose vitamin D supplementation was associated with significantly more women achieving and maintaining an optimal 25(OH)D. Among African American women, this was associated with reduced composite perinatal morbidity, demonstrating the importance of personalized vitamin D supplementation in pregnancy, particularly for populations at higher risk of deficiency.