BONE-DENSITY CHANGES DURING PREGNANCY AND LACTATION IN ACTIVE WOMEN - A LONGITUDINAL-STUDY

Six healthy active women, aged 28-34, had bone mineral density (BMD) measured (DPA & SPA) at seven sites prior to pregnancy, within 6 weeks of parturition, and after 6 months of lactation. Twenty-five nonpregnant women of the same age, height, weight, activity level and calcium intake were tested during the same period. Average calcium intake during pregnancy was 1526 mg/day; during lactation, 1622 mg/day. The nonpregnant women averaged 1756 mg/day. BMD decreased in the femoral neck (P less-than-or-equal-to 0.05) and radial shaft (P less-than-or-equal-to 0.05) during pregnancy but increased in the tibia (P less-than-or-equal-to 0.05). A 3.3% decrease in lumbar BMD during pregnancy returned to pre-pregnancy values during lactation. Bone loss at the femoral neck continued during lactation (P less-than-or-equal-to 0.05). Changes in BMD during pregnancy and lactation may represent changes in mechanical stress as a result of weight gain, changes in posture and/or activity, or some other factor specific to this population of active women.