Osteoporosis with vertebral fractures associated with pregnancy and lactation.

Three cases of young women who developed severe vertebral osteoporosis after pregnancy and during lactation are described. These patients shared several features: a low-calcium diet during most of their lives, very-low body weight in two patients, and a positive family history of osteoporosis in two patients. Initial studies disclosed vertebral fractures, severely diminished bone mineral density of the spine (Z score = -3.3 to -4.1), and a less severely affected bone mineral density of the hip (Z score = -1.6 to -2.3). During the prolonged follow-up of these patients, treated with oral biphosphonates, vitamin D, and calcium, an improved clinical response with a marked recovery of spine bone mineral density was observed. Poor general nutrition, low calcium intake, and a positive family history of osteoporosis appear to be strong risk factors for pregnancy- and lactation-associated osteoporosis. Although the mechanism of action is uncertain, calcium, vitamin D, and antiresorptive agents may have been beneficial in the treatment of this severe disorder.