Vitamin D is known for its role in calcium absorption and bone health, but interest in its role in reproduction has been growing. Vitamin D is known as the sunlight vitamin because it is synthesized in the skin in response to ultraviolet radiation. It can also be obtained from foods or nutritional supplements. Vitamin D is metabolized to 25-hydroxyvitamin D (25(OH)D) in the liver and this is the clinical biomarker of vitamin D status. Animal models of vitamin D deficiency show disrupted ovulation and subfertility. In human, community-based samples, we published three studies that have reported associations between low 25(OH)D and long or irregular menstrual cycles (PMID26997249, PMID 25879830) including one this past year in which we also reported delayed ovulation in women with low vitamin D (PMID 29337846). Similar to the animal studies, we recently found that high levels of 25-hydroxyvitamin D (25(OH)D), a biomarker of vitamin D status, were associated with a higher probability of becoming pregnant while low levels were associated with a lower probability of becoming pregnant (Human Reproduction, in press). In addition to vitamin D, we have continued our investigations of phthalates and BPA by examining their associations with early pregnancy events. We found that BPA and some phthalate metabolites were associated with early pregnancy events such as implantation timing, the initial rise in human chorionic gonadotropin, and the initial progesterone response to conception (PMID 30321738).
