Biotin is a water-soluble B vitamin with key roles in many aspects of human metabolism. As a cofactor of several carboxylases, biotin is required for gluconeogenesis, fatty acid synthesis, and leucine catabolism and may interact with histones to affect genome expression. Although the dietary requirement for biotin is unknown, an adequate intake level of 30 μg/d is recommended for healthy adults including pregnant women. Biotin deficiency appears to be common in human pregnancies and is teratogenic in animal models. Dietary biotin intake cannot be reliably assessed in pregnant women as food composition tables are incomplete. In addition, it is one of few essential nutrients that are absent in prenatal vitamins. The purpose of this review is to summarize the metabolic functions of biotin and highlight its role in fetal development through its carboxylase activities and putative effects on gene expression.