New research out of Qazvin University of Medical Science in Iran suggests that vitamin D during the third trimester of pregnancy can improve fetal growth. The new research was an open label randomized trial.
A few intervention studies have investigated the effect of vitamin D on fetal growth, and so far have found mixed results. Some studies show no effect on fetal growth while some show an improvement on fetal growth. Thus, we need more research to elucidate the relationship.
Iran provides a good place to study the relationship, because pregnant women are often deficient in vitamin D. It creates a unique opportunity for researchers to examine the benefits of making women sufficient in vitamin D and comparing them to the normal deficient population.
In the present study, researchers enrolled 130 women, randomizing 65 women to the vitamin D group and 65 to the control group. During the trial, the control group lost 11 women for various reasons while the vitamin D group lost 10 women.
The vitamin D group received 50,000 IU of vitamin D3 once per week for 8 weeks, starting around 26-28 weeks’ pregnant. The control group received a multivitamin containing 400 IU of vitamin D and 200 mg of calcium. It was open label, so both groups knew what they were taking.
After 8 weeks, the researchers looked at neonate (when the baby is born) head circumference and weight (both measures of fetal growth), as well as the mother’s weight. They compared these measures to the control group. Here is what they found:
- At the end of the trial, vitamin D levels improved in the vitamin D group to a mean level of 47.8 ng/ml from a baseline level of 15.9 ng/ml. The control group remained deficient, starting at baseline of 17.5 ng/ml and ending at 15.9 ng/ml.
- The neonates from the vitamin D group weighed significantly more than neonates from the control group. The vitamin D group neonates weighed a mean 3429 grams while the control group weighed a mean 3258 grams (p=.01).
- The neonates in the vitamin D group were significantly longer in length than the control group (49 verse 48.2 cm, p=.01).
- The neonates in the vitamin D group had significantly bigger heads, with head circumferences of 35.9 to 35.3 cm (p=.001).
- Pregnant mothers in the vitamin D group also gained more weight than the control group.
The researchers concluded,
“This study showed that treatment of pregnant women with vitamin D deficiency or insufficiency improves fetal growth indices (length, weight and head circumference) and increases maternal weight gain during pregnancy.”
Hashemipour S et al. This Effect of treatment of vitamin D deficiency and insufficiency during pregnancy on fetal growth indices and maternal weight gain: a randomized clinical trial. European Journal of Obstetrics & Gynecology and Reproductive Biology, 2013.