Two women, 31 and 19 years old, developed acute back pain with non-traumatic vertebral fractures one month after delivery in one case, and during the 9th month of gestation in the second case. For the first patient, the evolution was favorable with an increase of bone mineral density (15.2% over fourteen months under calcium and vitamin D). Ten years later, the osteoporosis of the second patient worsened without any new pregnancy. Our observations suggest the possibility of different pathogenies in pregnancy-associated osteoporosis.