Young women who take hormonal birth control pills that contain estrogen may have enhanced levels of vitamin D in their blood. However, if they decide to quit using them in order to become pregnant, those levels can drop — at least according to a recent study published in the Journal of Clinical Endocrinology & Metabolism.
Dr. Quaker Harmon from the National Institute of Environmental Health, Research Triangle Park, NC and colleagues evaluated the Vitamin D status of nearly 1700 African-American women living in the Detroit, MI vicinity. All were 23-24 years of age. As part of a study on uterine fibroids, the women had given blood samples, which were then analyzed for vitamin D content.
The authors adjusted for changes in exposure to the sun, since that can increase vitamin D levels. They then found that women who were using hormonal contraceptive pills had, on average, a twenty percent higher level of vitamin D than women who weren't on the pills. While interesting in itself, these data suggest that when a woman stops taking hormonal contraception, her levels of vitamin D may decrease. This can be problematic if the levels drop enough so that they are not adequate for fetal development.
Dr. Harmon was quoted: "Our findings indicate women may run the risk of developing vitamin D deficiency just when they want to become pregnant. For women who are planning to stop using birth control, it is worth taking steps to ensure that vitamin D levels are adequate while trying to conceive and during pregnancy."
While this study is relatively small, and cross-sectional, it is worth some attention from women and their healthcare providers — it's important that pregnant women have adequate levels of vitamin D before and during gestation.