Purpose of review: At birth, the fetus will contain 30 g of calcium; during the third trimester the calcium accrual can be up to 340 mg/day. Therefore, extremely high demands for calcium provision are placed upon the mother. This review aims to describe the adaptive mechanisms of the female skeleton to pregnancy and lactation, which ensure optimal fetal skeletal mineralization without compromise to maternal bone strength.
Recent findings: Descriptions of changes in bone status during pregnancy and lactation have been published. One of the only studies to measure pre-conception to post-weaning shows complete recovery of maternal spinal bone mineral density (BMD) and near recovery at the hip. Most studies describe trabecular bone loss, but there is evidence for endosteal resorption of the metacarpals. In a retrospective study of former teenage mothers those who breastfed had similar hip BMD to nulliparous age-matched women; those who did not breastfeed had lower hip BMD. Maternal response to low calcium intake differs from that of normal calcium intake.
Summary: Pregnancy and lactation do not have an overall negative effect upon the maternal skeleton. Retrospective evidence suggests no harmful effect of teenage pregnancy if the teenager breastfed, but this requires further investigation. The effects of other situations, for example low vitamin D status or low calcium intake, require further research to inform future clinical practice.