Osteoporosis associated with pregnancy and lactation: bone biopsy and skeletal features in three patients.

Case reports of three young patients who developed vertebral fractures and skeletal complications during pregnancy and/or lactation are presented. Radiologic features are described. All three had severe disease with three to nine vertebral fractures at presentation postpartum. In two patients, follow-up for 5-7.8 yr (including further pregnancy in each) revealed no further fractures. In general, serum and urine features were normal, the exceptions being a low serum 25-hydroxyvitamin D level (plus intermittent elevation of serum parathyroid hormone) in one, a tendency to low plasma alkaline phosphatase in another, and in the third (the most severely affected patient) a transient rise in urinary hydroxyproline and plasma alkaline phosphatase during a phase of bone loss following her second and third pregnancies. Bone biopsies performed 1 to 6-1/2 yr after parturition showed quantitative bone histologic features and bone formation rates that, as a group, were not significantly different from either normal or postmenopausal osteoporotic subjects. These patients did not have osteomalacia and did not show high turnover osteoporotic features. It is possible that this type of osteoporosis may be somewhat self-limiting, although this hypothesis is subject to great influence by any adaptive lifestyle changes introduced by the patient. The severe fracture history of these patients emphasizes the gravity of their bone disease and stresses the need for further study on the etiology and treatment of this form of osteoporosis.