INTRODUCTIONThe exact amount of vitamin D required for pregnant women to adequately supply the foetus during pregnancy is still unclear. This randomised trial attempted to determine the optimal dose of vitamin D necessary during pregnancy in order to attain a vitamin D level > 20 ng/mL in neonates.

METHODSA total of 51 healthy, pregnant women in Yazd, Iran, were recruited in 2009. Of these, 34 were randomised to receive either 50,000 IU (Group A) or 100,000 IU (Group B) of vitamin D3 per month from the second trimester of pregnancy. The remaining 17 pregnant women, who formed the third group (Group C) and were found to have vitamin D deficiency, were initially treated with 200,000 IU of vitamin D3, following which the dose was adjusted to 50,000 IU per month. 25-hydroxyvitamin D (25[OH]D) in cord blood was measured by chemiluminescence immunoassay, and a serum 25(OH)D level < 20 ng/mL was defined as deficiency.

RESULTSAll the pregnant women had a vitamin D level < 30 ng/mL at the beginning of the second trimester. The neonates of 76% of women from Group A had sufficient levels of 25(OH)D. All the neonates born to women in Groups B and C had 25(OH)D > 20 ng/mL. No side effects were observed in our participants during the period of vitamin D supplementation.

CONCLUSIONA vitamin D3dose > 50,000 IU/month is required during the second and third trimesters of pregnancy for vitamin D-deficient pregnant women in order for their neonates to achieve serum 25(OH)D levels > 20 ng/mL. Supplementation with < 50,000 IU/month is insufficient to ensure a vitamin D level > 20 ng/mL in all neonates born to vitamin D-deficient pregnant women.