A case-control study of hip fracture in black and white women of age 45 and older was conducted in New York City and Philadelphia from 1987 to 1992. The relationship between reproductive and related factors and hip fracture was examined in the present analyses. Women hospitalized with their frrst hip fracture (175 whites, 144 blacks) were compared to two sets of controls, one hospital- (165 whites, 181 blacks) and one community-based (201 whites, 218 blacks). The controls were matched to the cases on age, race, and zip code (for cases age 65 and older) or telephone exchange (for cases younger than age 65) for the community controls, and age, race, date of admission, and hospital for the hospital controls. Information on potential risk factors was obtained by structured questionnaire.

Never having been pregnant and never having had a livebirth may be associated with increased odds of hip fracture for whites and blacks. No association was found between number of pregnancies or livebiiths and odds of hip fracture among white women. Increasing number of pregnancies appeared to be inversely related to hip fracture odds among black women, and the relation persisted after excluding nulligiavid women. Several other reproductive variables (ages at first pregnancy and livebiith, induced and spontaneous abortions, lifetime duration of breastfeeding, average duration of breastfeeding per child, proportion children breastfed) had no influence on the odds of hip fracture for whites or blacks.

Early age at menopause and premenopausal bilateral oophorectomy were not associated with increased odds of hip fracture for whites or blacks. Estrogen replacement therapy did not reduce hip fracture odds among white women. Among black women, estrogen use for at least one year decreased hip fracture odds among those less than 75 years of age.

In summary, there was little evidence that reproductive characteristics other than nulligravidity affect hip fracture risk for black or white women. Estrogen replacement therapy protected against hip fracture for black women less than age 75 years, but no such association was found for white women.