Hormone replacement therapy for bone protection in multiparous women: when to initiate it

Hormone replacement therapy is used in postmenopausal women to improve symptoms of menopause and to protect bone and the cardiovascular system. We have evaluated the effects of parity in terms of number of deliveries on bone density and fracture risk at different ages.

We evaluated 1875 Hispanic women > or =50 years old (61.3 +/- 8.3 years), 425 with a history of nonselective fractures and 1450 without previous fractures. Body mass index was 27.3 +/- 4.3 kg/m(2). Bone mineral densities were determined for the total body in 1468 cases, the femur in 221 cases, and the lumbar spine in 189 cases. Women were classified according to lifetime number of deliveries (from 0 to > or =5), and bone mineral densities and odds ratios for fracture risk were calculated relative to the number of deliveries.

Bone mineral densities in total body, pelvis, and legs and total calcium and total mineral contents increased (P <.001) with > or =2 deliveries among women 50 to 59 years old but not among those > or =70 years old. The prevalence of fractures was higher in nulliparous than in multiparous women at all ages. Fracture risk was lower in multiparous women at all age groups, including those > or =70 years old (odds ratio, 0.47; 95% confidence interval, 0.26-0.84; P <.006).

Bone mineral density increases with the number of deliveries until the age of 69 years. Fracture prevalence and fracture risk are lower among multiparous women even at older ages. These findings suggest that hormone replacement therapy can be delayed until 65 years of age for multiparous women but should be initiated at the beginning of menopause for nulliparous women.