Prevalence of low vitamin D levels in an urban midwestern obstetric practice.

INTRODUCTION: This study describes the prevalence of low vitamin D levels in pregnancy in a diverse urban population.
METHODS: This was a retrospective chart review of 2839 women who gave birth at a Michigan hospital between January 1, 2008 and December 31, 2009 and had at least 1 vitamin D (25-hydroxyvitamin D [25(OH)D]) measurement during their pregnancies. Race/ethnic group, wearing the hijab, and season of 25(OH)D sample collection were used in the descriptive analysis.
RESULTS: Most women (92.5%) in this study had documented insufficient levels of 25(OH)D (defined as < 30 mL), and 71.7% of all women had deficient levels of 25(OH)D (defined as < 20 ng/mL). Subgroups with the highest percentage of women who were vitamin D deficient were: Middle Eastern (91.8%), African American (81.6%), and Asian (74.3%). Overall, women who wore the hijab were more likely to be deficient (89.5% vs 68.7; P < .0001) and insufficient (98.8% vs 91.4%; P < .0001) compared with women who did not wear the hijab. DISCUSSION: The data demonstrate the high rate of vitamin D deficiency and insufficiency in this white and nonwhite urban population in which samples were collected in both winter and nonwinter months. The percentage of woman who had 25(OH)D levels below 30 ng/mL was significantly higher than that reported in the National Health and Nutrition Examination Survey III (NHANES III) (92.5% compared to 69%), although NHANES did not sample women in northern climates in the winter months. Even using new diagnostic definitions for vitamin D deficiency from the Institute of Medicine, the proportion of women with vitamin D deficiency and insufficiency was 40% and 31.6%, respectively. Clinicians caring for women in northern climates as well as women who are Middle Eastern, African American, and Asian need to be aware of the risk for vitamin D deficiency and the potential health effects for the mother and infant.