Vitamin D in pregnancy: High daily dose may improve infant outcomes
A high daily dose of vitamin D (4,000 IU/day) resulted in a reduction in vitamin D deficiency in pregnant women, coupled with a lower risk of preterm births and low birth weight in their newborns, according to a study presented at RCOG 2018.
According to Assistant Professor Sidrah Nausheen from the Aga Khan University in Karachi, Pakistan, previous research has alluded to a high prevalence of vitamin D deficiency in pregnant women and their newborn infants. [Int J Gynaecol Obstet 2011;112:229-233]
“[Thus], assessment of dose of vitamin D is critical during pregnancy to provide the foetus and neonate with adequate vitamin D stores during development and growth. The current recommended daily intake of 400 IU/day is not sufficient to prevent complications and hypovitaminosis,” said Nausheen.
In this double-blind, hospital-based trial conducted at the Aga Khan University Hospital in Kharadar, Pakistan, researchers randomized 350 women aged 15–45 years (mean age 26.0 years) with singleton pregnancies at <16 weeks gestation to receive vitamin D in doses of 400, 2,000, or 4,000 IU/day (n=115, 115, and 120, respectively), with the 400 IU/day dose serving as the control group. The final number of women assessed was 272.
Women with multiple pregnancies and those with pre-existing type I or type II diabetes or hypertension were excluded.
A blood sample was taken at time of recruitment and assessed for vitamin D, calcium, phosphorus, and alkaline phosphatase levels, while another sample was taken at time of delivery to assess for vitamin D status.
About 50 percent of the women were determined as acquiring adequate sunlight, with 96.3 percent of women wearing a veil or burqa when outdoors.
Higher doses of vitamin D significantly reduced the incidence of vitamin D deficiency (<20 ng/mL), decreasing from 97.5 percent of women at baseline to 40 percent following 4,000 IU/day, 94.8 percent at baseline to 82 percent following 2,000 IU/day, and 96.4 percent at baseline to 91.2 percent following 400 IU/day. [RCOG 2018, abstract 6914]
Women who received a 4,000 IU/day dose of vitamin D had a lower risk of preterm birth (≤37 weeks gestation) compared with women who received the 400 IU/day dose (5.6 percent vs 17.6 percent, odds ratio [OR] 0.61, 95 percent confidence interval [CI], 0.46–0.82; p=0.05).
Women on 4,000 IU/day also had a lower risk of delivering infants with low birth weight (≤2.5 kg) than those on 400 IU/day (5.6 percent vs 20.9 percent, OR, 0.57, 95 percent CI, 0.44–0.75; p=0.01).
Risk of pre-eclampsia or gestational diabetes did not significantly differ between women on different vitamin D doses (p=0.99 and 0.70, respectively). There was no incidence of stillbirth in this study population.
“Our study findings provide evidence that high dose of vitamin D [4,000 IU/day] has a significant impact on reduction of vitamin D deficiency among mothers [with] no adverse event reported during the study,” said Nausheen.
“There [was] significant reduction in preterm births and low birth weight babies although no effect on pre-eclampsia [or diabetes] was seen,” she said, calling for larger randomized trials to confirm these findings.