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Rickets (rachitic pelvis) was a common cause of death in childbirth in industrialized nations at the turn of the 20th century and associated with a steep rise in cesarean section rates. The addition of vitamin D to milk caused the virtual disappearance of rickets, but recent reports suggest that vitamin D deficiency is now widespread in industrialized nations. In 2 previous studies, a high incidence of vitamin D deficiency was found in pregnant and lactating women. Another study reported that 50% of mothers and 65% of newborns infants were severely vitamin D deficient (25-hydroxyvitamin D [25(OH)D: Ͻ30 nmol/L]) at the time of birth despite drinking vitamin D fortified milk and taking a prenatal vitamin D supplement. It is possible that deficiency of this vitamin may play a role in the nearly 50% increase in primary cesarean sections in the last decade.This study investigated the association between serum concentrations of maternal vitamin D (serum 25(OH)D) at birth and the frequency of primary cesarean section among 253 women enrolled at an urban teaching hospital. Demographic and medical data were obtained from maternal medical records. Maternal serum 25(OH)D was measured within 72 hours of delivery. Serum 25(OH)D was a proxy for vitamin D status. Maternal vitamin D deficiency was defined as serum 25(OH)D less than 37.5 nmol/L (15 ng/mL). Multivariable logistic regression analysis was used to adjust the data for several variables, including race, age, education level, insurance status, and alcohol use.Of the 253 study subjects, 43 (17%) had a primary cesarean section. The frequency of cesarean section and levels of serum 25(OH)D had an inverse association. In unadjusted analysis, more than twice as many women with serum 25(OH)D less than 37.5 nmol/L had a primary cesarean section compared to those with 25(OH)D 37.5 nmol/L or greater (P ϭ 0.012). Multivariate logistic regression analysis showed that a primary cesarean section in women with vitamin D deficiency was nearly 4 times more likely compared to women without deficiency (adjusted OR, 3.84; 95% CI, 1.71-8.62).These findings show a clear association between vitamin D deficiency and increased likelihood of primary cesarean section and suggest the need for a randomized trial to determine whether additional vitamin supplementation could reduce the cesarean section rate. EDITORIAL COMMENT(The abstracted article of Merewood et al was simply too provocative to pass up. Without statistical adjustment, women with vitamin D concentrations of Ͻ37.5 nmol/L (i.e., deficiency as defined by the Centers for Disease Control and Prevention) were twice as likely to undergo primary cesarean as women with higher vitamin D concentrations, 28% versus 14%. With adjustment for potential confounders, they were almost 4 times as likely! The authors enthusiastically conclude that "A randomized clinical trial is now needed to determine whether adequate vitamin D supplementation during pregnancy to raise blood levels of 25(OH)D above at least 37.5 nmol/L can reduce the cesarean section ...

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