Pregnancy-associated osteoporosis: Does the skeleton recover?

Osteoporosis in pregnancy is a rare clinical problem of unknown cause. If t he bone loss results from the pregnancy alone it should improve toward norm al after delivery; in contrast, where bone density was low before pregnancy , due to some other secondary cause, significant postpartum improvement mig ht not be expected. Thirteen women (age 23-37 years) with pregnancy-associa ted osteoporosis presenting with either pain in the back and vertebral coll apse (8 subjects) or pain in the hip (5 subjects) had consecutive dual-ener gy X-ray absorptiometry measurements of bone mineral density (BMD) for up t o 8 years after an affected pregnancy. The BMD results were expressed as a Z-score in relation to an age-matched mean. The mean initial (0-6 months po stpartum) BMD was low in both groups and at both sites. In the back pain gr oup the mean spine Z-score (LI-LA) was -3.34 (range -2.25 to -4.66) and mea n total hip Z-score was -2.41 (range -1.44 to -3.82). In the hip pain group the mean spine Z-score was -2.00 (range -1.48 to -2.65) and mean hip Z-sco re was -2.19 (range -1.12 to -3.26). Subsequent mean hip and spine BMD incr eased significantly toward the lower end of the normal range. We conclude t hat a reversible part of the bone loss is related to the pregnancy itself. A low BMD before pregnancy cannot be excluded. Knowledge that the bone dens ity increases after an affected pregnancy, combined with the known rarity o f recurrent symptoms in subsequent pregnancies, is important in prognosis.