the effects of vitamin d supplementation on maternal and neonatal outcome: a randomized clinical trial

background: vitamin d supplementation during pregnancy has been supposed to defend against adverse gestational outcomes. objective: this randomized clinical trial study was conducted to assess the effects of 50,000 iu of vitamin d every two weeks supplementation on the incidence of gestational diabetes (gdm), gestational hypertension, preeclampsia and preterm labor, vitamin d status at term and neonatal outcomes contrasted with pregnant women that received 400 iu vitamin d daily. materials and methods: 500 women with gestational age 12-16 weeks and serum 25 hydroxy vitamin d (25 (oh) d ) less than 30 ng/ml randomly categorized in two groups. group a received 400 iu vitamin d daily and group b 50,000 iu vitamin d every 2 weeks orally until delivery. maternal and neonatal outcomes were assessed in two groups. results: the incidence of gdm in group b was significantly lower than group a (6.7% versus 13.4%) and odds ratio (95% confidence interval) was 0.46 (0.24-0.87) (p=0.01). the mean ± sd level of 25 (oh) d at the time of delivery in mothers in group b was significantly higher than a (37.9 ± 19.8 versus 27.2 ± 18.8 ng/ml, respectively) (p=0.001). there were no differences in the incidence of preeclampsia, gestational hypertension, preterm labor, and low birth weight between two groups. the mean level of 25 (oh) d in cord blood of group b was significantly higher than group a (37.9 ± 18 versus 29.7 ± 19ng/ml, respectively). anthropometric measures between neonates were not significantly different. conclusion: our study showed 50,000 iu vitamin d every 2 weeks decreased the incidence of gdm.