BONE-MINERAL CHANGES DURING PREGNANCY AND LACTATION - A LONGITUDINAL COHORT STUDY

1. The influence of pregnancy, lactation and weaning on bone mineral d ensity in healthy women was investigated during a 2 year prospective s tudy of 59 pregnant and lactating women from the 18th week of gestatio n. 2. Bone mineral density was measured by dual energy X-ray absorptio metry at the non-dominant radius ultra distally and more proximally in the 18th and 37th weeks of gestation, and 0, 3, 6, 12 and 18 months a fter delivery. Measurements of bone mineral density of the lumbar spin e, the proximal femur and the whole body were performed at all dates a fter delivery. 3. Reappearance of menstruation after delivery averaged 6.1 months; mean lactating period was 8.7 months. During pregnancy an d lactation bone mineral density tended to decrease, but different mea suring sites show ed different patterns of bone mineral density change s. The reduction in the ultra distal radius during pregnancy amounted to 296, and no further changes were observed here during lactation. Af ter delivery, reduction in mean bone mineral density was most pronounc ed in the spine (5.2% in 3 months), but the fall in bone mass tended t o revert after resumption of menstruation. Bone mineral density was st ill reduced by 3.3% after 12 months in cr omen with menstruation resum ption later than 8 months after delivery. No significant reduction was observed 18 months after delivery, No association with calcium intake , weight changes or initial bone mineral density was observed. High ca lcium intake did not protect against bone mineral loss in the spine an d the femur. 4. Thus it can be concluded that bone loss during pregnan cy and lactation took place mainly from the trabecular skeleton. Resum ption of menstruation tended to result in a regain of bone mass toward s baseline.