Adaptations in mineral metabolism occur during pregnancy and lactation, and these adaptations uniquely affect the presentation, diagnosis, and management of disorders of calcium and bone metabolism. Maternal adaptations to pregnancy and lactation have evolved differently over time, such that dietary calcium absorption dominates in pregnancy, whereas the temporary borrowing of calcium from the skeleton dominates during lactation. Lactation produces an obligatory skeletal calcium loss regardless of maternal calcium intake, but the calcium is restored to the skeleton after weaning through mechanisms that are not understood. Although some women experience fragility fractures as a consequence of pregnancy or lactation, for most women, the changes in calcium and bone metabolism during pregnancy and lactation are normal and without adverse consequences in the long-term.