Bone loss in adolescent and adult pregnant women

Objective: To determine the amount of change in bone ultrasound measures am ong pregnant adolescent girls and women and whether that change was associa ted with adolescence, maternal growth during pregnancy, limited weight gain during pregnancy, hypertension in pregnancy, or poor diet. Methods: We used bone ultrasound measurements of attenuation and sound velo city to assess changes in quantitative ultrasound indices of 252 pregnant a dolescent girls and women age 12-34 years. Bone ultrasound measurement of t he os calcis was performed at 16 +/- 7 weeks' gestation (mean +/- standard deviation and 6 +/- 1 weeks postpartum. Results: On average, the bone quantitative ultrasound index was 3.6% lower 6 weeks postpartum than at entry into care (P < .001). Nulliparous patients had significantly greater bone loss than did parous subjects. Still-growin g adolescents had greater quantitative ultrasound index decreases than did grown women (-5.5% versus -1.9%, P < .02). Patients in the upper tertile of baseline quantitative ultrasound index lost more bone than did patients in the lower tertile (-5% versus 0.5%, P <.02). Pregravid weight weight chang e during pregnancy, gynecologic age, and age at menarche predicted bone cha nge in subgroups defined by parity or age; however, none of the differences in those variables were statistically significant Greater dietary calcium intake, less physical activity, and pregnancy hypertension and preeclampsia were not associated with bone change. Conclusion: There has been inconsistent evidence of maternal bone loss duri ng pregnancy. The findings of this study challenge the assumption that beca use of increased calcium absorption from the maternal intestine, no transit ory bone loss occurs in pregnancy. The amount of bone loss among growing ad olescents and nulliparous patients was consistent with the demands of fetal mineralization and the continued demands of the maternal skeleton during g rowth. (C) 2000 by The American College of Obstetricians and Gynecologists.