Pregnant women with vitamin D deficiencies are more likely than other expectant moms to deliver their babies via cesarean section.

"Women with a vitamin D deficiency were almost 4 times more likely to have a cesarean than those with [normal] vitamin D levels," says senior study author Anne Merewood, an assistant pediatrics professor at Boston University School of Medicine. "Vitamin D is definitely involved in muscle strength…. contractions of the uterus [which is made of smooth muscle] may not be performing as well as they could be," making it difficult for the woman to help push the baby out herself.

This research was actually part of a larger study (the findings of which are yet to be published) of the prevalence of vitamin D deficiencies among women of childbearing age. Merewood told ScientificAmerican.com that 156 (36 percent) of the 433 women in the larger study were found to be vitamin D deficient and 100 (23 percent) severely deficient. This translates into a potentially major public health problem, as vitamin D deficiency was recently linked to a number of chronic diseases, including cancer and multiple sclerosis.

Merewood's advice to pregnant women: Be careful in the sun but be sure to get some exposure since its rays help produce vitamin D in the body. She says that women should consider drinking vitamin D-fortified milk, taking vitamin D supplements and, for those at high risk (women with minimal sun exposure or dark-skinned women living at high latitudes) asking their docs for blood tests to make sure they're not deficient in the bone and muscle-building vitamin. 

But no need to panic, says Daniel Hirsch, an assistant pediatrics prof at the Robert Wood Johnson Medical School in Somerville, N.J.

"There could be multiple reasons that are combining to explain why they happened to find an association between  . . . C-sections and vitamin D deficiency," he says. "Maybe the moms who had lower [vitamin] D levels happened to be delivered by OBs [obstetrician-gynecologists] who themselves are more likely to section a woman." Hirsh says that more large-scale studies with are needed to verify this apparent link between vitamin D deficiency and C-sections.

In this study, researchers tested the vitamin D levels of healthy pregnant women within 72 hours of delivering; 43 (17 percent) of them had first-time C-sections (those with prior C-sections were eliminated from the study, because they are more likely to have repeat such deliveries).

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