Potential benefits of vitamin D supplementation on pregnancy

The level of vitamin D in pregnant women and the effect of vitamin D supplementation are lack in Taiwan.

To investigate the vitamin D serum level and the effect of its supplementation on pregnancy.

We included 1048 pregnant women who underwent prenatal exam with known serum 25-hydroxyvitamin D3 [25(OH)D3] levels and delivery at the Mackay Memorial Hospital, Taipei, Taiwan during 2015-2018. A daily dose 2000 IU of vitamin D was given, starting at 12-16 weeks of pregnancy, to reach the level of 20 ng/mL, and then a maintenance dose of 800 IU/day was given. The other 3654 women without vitamin D supplementation delivered in 2018 served as control group. Pregnancy outcomes were recorded for analysis.

Over 80% of the 1048 pregnant women were vitamin D deficiency. There was an inverse correlation between serum vitamin D levels and maternal body mass index (p = 0.0366). We compared 375 women with serum vitamin D levels increased above 30 ng/mL after supplementation with control group. The rates of preterm birth, low birth weight, and postpartum hemorrhage between these 2 groups were 6.67% vs. 11.19% (p = 0.007), 6.40% vs. 10.0% (p = 0.025), and 1.33% vs. 3.20% (p = 0.04), respectively.

Vitamin D deficiency is very prevalent in pregnant women, especially those with high BMI, in Taiwan. It can be corrected by adequate vitamin D supplementation, which may decrease the risk of pregnancy complications and bring benefits to the fetus.