RCT: Are vitamin D levels associated with pregnancy outcomes?

Posted on: February 26, 2015   by  Amber Tovey

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A recent randomized controlled trial has provided more evidence that vitamin D supplementation reduces the risk of maternal comorbidities and improves health outcomes in infants.

Nutrition plays a vital role in ensuring that a newborn develops properly. Accordingly, there is a large market for prenatal supplements. Despite the high use of prenatal supplements, pregnant women, neonates, and infants are at a high risk for vitamin D deficiency, putting them at an increased risk of heath complications.

Studies have demonstrated that maternal vitamin D levels are related to the risk of preeclampsia, preterm birth, gestational diabetes, and infections.

Clinical trials have shown that supplementation with the recommended dietary allowance (RDA) of 400 IU does not improve the vitamin D status of pregnant women. Higher dosages have been given in some studies involving vitamin D supplementation in pregnant women, but only a small percentage of women in these studies achieve sufficient levels.

In the present study, researchers from India evaluated the effects of vitamin D supplementation on maternal complications. They recruited 180 pregnant women and divided them into two groups, with 120 women in the intervention group and 60 women in the non-intervention group.

The researchers first measured the baseline vitamin D levels of the women. Then, women from the intervention group were supplemented with vitamin D based on their vitamin D status classification. Women with vitamin D levels above 20 ng/ml were classified as sufficient. Levels between 10 ng/ml and 20 ng/ml were considered insufficient, and deficient status was defined as levels less than 10 ng/ml.

The overall prevalence of vitamin D insufficiency and deficiency among the pregnant women was 77.5% at baseline.

Women with sufficient levels of vitamin D received only one 60,000 IU bolus dose of vitamin D at 20 weeks, women who were insufficient received two bolus doses of 120,000 IU at 20 and 24 weeks and women with deficient levels received four bolus doses of 120,000 IU of vitamin D at 20, 24, 28, and 32 weeks.

The researchers were interested in the effects of vitamin D supplementation on risk of maternal complications and infant health outcomes. They specifically looked at preterm labor, pre-eclampsia, gestational diabetes, low birth weight, and APGAR scores as the outcomes.

APGAR score is a scale to assess the health of the newborn baby immediately after birth. APGAR stands for the five aspects that the scale assesses: appearance, pulse, grimace, activity, and respiration.

Did supplementation achieve vitamin D sufficiency in the intervention group? Were vitamin D levels associated with maternal complications and the infant’s health? Here is what the researchers found:

  • Despite receiving a total of 480,000 IU of vitamin D, only 52.8% of the pregnant women who were considered deficient at baseline achieved sufficiency at delivery.
  • In the intervention group, 85.1% of women who were considered insufficient and 89% of women who were sufficient achieved sufficiency at delivery.
  • Newborns of mothers who supplemented had higher cord blood levels of vitamin D compared to newborns of mothers who did not supplement.
  • Pregnancy complications, including preterm labor, pre-eclampsia, or gestational diabetes mellitus were seen in 44% of the women in the non-intervention group compared to 20.4% of women in the intervention group.
  • A significant decrease in incidence of preterm labor was seen in the intervention group (p = 0.02).
  • In the intervention group, 8% of the babies were small for gestational age compared to 19.2% of the babies in the non-intervention group (p = 0.04).
  • Among moms from the non-intervention group, 21.1% had pre-eclampsia, compared to 11.1% of the moms from the intervention group. However, this difference was not statistically significant (p = 0.08).

The researchers concluded,

“High dose vitamin D supplementation therapy in pregnancy can help in reducing the incidence of gestational hypertension/preeclampsia, preterm labor/births; and have a beneficial effect on the neonates.”

They stated,

“All women need to be given supplemental vitamin D during pregnancy, as there is inadequate sun-exposure as well as dietary intake of vitamin D in the majority.”

This study adds further emphasis on the importance of vitamin D supplementation during pregnancy.

There are several strengths of this study to acknowledge. First, the researchers used the gold standard for study designs, a randomized controlled trial. This limits bias and the effect of potential confounding factors on the results. Another strength to highlight is that supplementation was based on baseline vitamin D levels.  However, only about half of the women achieved sufficiency from the supplementation group.

Further studies should use higher and more frequent dosages and achieve greater rates of sufficiency in the intervention group.  Also, it will be necessary at some time to see if daily dosing of vitamin D is better than bolus dosing.

Source

Sablock A., et al. Supplementation of Vitamin D in pregnancy and its correlation with feto-maternal outcome. Clinical Endocrinology, 2015.

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