By Joene Hendry

NEW YORK (Reuters Health) - Women with insufficient vitamin D intake during pregnancy may be at increased risk for birth by cesarean section, study findings suggest.

Of 253 women who gave birth in a Boston, Massachusetts hospital, those deficient in vitamin D were nearly 4-times more likely to deliver by cesarean section than women with higher levels of vitamin D, report Dr. Michael F. Holick and colleagues.

"Vitamin D is critically important for muscle function," Holick, of Boston University School of Medicine, told Reuters Health.

Thus, it is not at all surprising that pregnant women, who are at very high risk for vitamin D deficiency, have an associated increased risk for cesarean birth, Holick said.

Individual vitamin D levels vary according to supplementation and the skin's ability to convert direct sunlight exposure to 25-hydroxyvitamin D in blood.

In this study, Holick and colleagues assessed post-delivery blood vitamin D levels among women who were about 25 years old on average and lived in the Boston area for their entire pregnancy.

One-hundred thirty of the women were Hispanic, 29 were non-Hispanic white, and 94 were non-Hispanic black, the researchers report

Holick's group defined vitamin D deficiency at the Centers for Disease Control and Prevention level of less than 37.5 nanomoles per liter (15 nanograms per milliliter) of 25-hydroxyvitamin D in blood.

According to a report in the Journal of Clinical Endocrinology and Metabolism, the investigators noted cesarean delivery among 28 percent of the women deficient in vitamin D, but in just 14 percent of those with vitamin D levels above 37.5 nanomoles per liter.

Holick's team also noted lower average vitamin D levels among women who had cesarean versus vaginal delivery.

In a separate study, Holick's team identified vitamin D deficiency among more than three-quarters of moms and newborns despite the moms' daily ingestion of prenatal vitamins and 2 glasses of milk during pregnancy.

Holick and colleagues call for further investigations to determine whether increasing vitamin D intake among pregnant women will reduce cesarean delivery rates.

SOURCE: Journal of Clinical Endocrinology and Metabolism, April 2009

Related MedlinePlus Pages:

• Cesarean Section
• Vitamins