Pregnant women who are vitamin D deficient are at an increased risk for delivering a baby by caesarean section, say researchers.

Over a two-year period, experts from Boston University School of Medicine (BUSM) and Boston Medical Centre (BMC), analyzed the relationship between maternal serum 25-hydroxyvitamin D [25(OH)D] and the prevalence of primary caesarean section.

In total, 253 women were enrolled in this study, of whom 43 (17 per cent) had a caesarean section. The researchers found that 28 per cent of women with serum 25(OH)D less than 37.5 nmol/L had a caesarean section, compared to only 14 per cent of women with 25(OH)D greater than 37.5 nmol/L.

"In our analysis, pregnant women who were vitamin D deficient at the time of delivery had almost four times the odds of caesarean birth than women who were not deficient," said senior author Michael Holick, MD, PhD, director of the General Clinical Research Centre and professor of medicine, physiology and biophysics at BUSM and Anne Merewood assistant professor of paediatrics at BUSM and lead author of the study.

According to Holick, one explanation for the findings is that vitamin D deficiency has been associated with proximal muscle weakness as well as suboptimal muscle performance and strength.

The study has been published in the Journal of Clinical Endocrinology & Metabolism.