The Effect of Pregnancy on Bone Density and Bone Turnover

During pregnancy, the mother adapts to meet the calcium demands of the fetus. The effect of this adaptation on the maternal skeleton is not fully understood. Our objectives were to evaluate changes in bone mineral density (BMD) and bone turnover during pregnancy. We studied 16 women longitudinally, with baseline measurements before pregnancy; then at 16, 26, and 36 weeks of pregnancy; and postpartum. We measured total‐body BMD and biochemical markers of bone resorption (urinary pyridinium crosslinks and telopeptides of type I collagen) and bone formation (serum bone alkaline phosphatase, propeptides of type I procollagen [PINP] and osteocalcin). We also measured parathyroid hormone (PTH), insulin‐like growth factor I (IGF‐I), and human placental lactogen. Postpartum, BMD increased in the arms (2.8%, P< 0.01) and legs (1.9%, P< 0.01) but decreased in the pelvis (−3.2%, P