Most Pregnant Women Low in Vitamin D

AURORA, Colo. Seven out of every ten pregnant women in the United States are not getting enough vitamin D, according to a study published in the May issue of the American Journal of Obstetrics and Gynecology. A press release from the University of Colorado Denver School of Medicine, researchers noted the study found prenatal vitamins raise vitamin D levels during pregnancy, but higher doses may be needed for many women.

This research was supported by the National Institutes of Health. The study team from University of Colorado School of Medicine, Massachusetts General Hospital and Childrens Hospital Boston analyzed nationally representative data from 928 pregnant and 5,173 non-pregnant women of childbearing age collected by the Centers for Disease Control and Prevention.

The study showed many pregnant women in the United States have insufficient vitamin D levels. For those women, prenatal vitamins do not provide enough vitamin D and higher doses are needed to raise levels. Women with darker skin, those who cover their skin for religious or cultural reasons, and those living farther north during winter months are at particularly high risk for lower vitamin D levels, according to the university. 

Prenatal vitamins do help raise vitamin D levels, but many women start taking them after becoming pregnant, said Adit Ginde, MD, MPH, assistant professor at University of Colorado Denver School of Medicine and lead author of the study. Although research is ongoing, I think its best for women to start a few months before becoming pregnant to maximize the likely health benefits.

Ginde added, We already know vitamin D is important for bone health of the mother and infant, but we are just starting to scratch the surface about the many potential health benefits of vitamin D during pregnancy.

Vitamin D deficiency early in life has been linked to increased risk of childhood wheezing and respiratory infections. Lower levels in adults have been linked to cardiovascular disease and cancer.

The study found some women have enough Vitamin D, and Ginde cautioned against excessive vitamin D intake. We need more data from clinical trials of vitamin D supplementation in pregnant women. If the ongoing trials continue to show benefit, the best strategy will likely be measuring vitamin D levels through a simple blood test and choosing supplementation doses according to those levels. This tailored approach is common in preventive care for people with high cholesterol, and safer and more effective than a one-size-fits-all solution.