Long-term fracture risk among infertile women: A population-based cohort study

Nulliparity has been linked to bone loss and fractures, but the contributio n of infertility is unclear. The purpose of this study was to assess the lo ng-term risk of fractures among infertile women. In a population-based retr ospective cohort study, all 658 Olmsted County, Minnesota, women with infer tility (failure to conceive after 1 year despite intercourse without contra ception) first diagnosed at Mayo Clinic in 1935-1964 were followed for frac tures. Risk was assessed by comparing new fractures of each type to the num ber expected from sex-specific and age-specific fracture rates in the gener al population (standardized incidence ratios [SIR]). During 18,130 person-y ears of follow-up, 184 women experienced at least one fracture when 291 wou ld have been expected on the basis of fracture incidence rates in the gener al population (SIR 0.6, 95% CI 0.5-0.7). There was no increase in proximal femur fractures (SIR 1.0, 95% CI 0.6-1.6) and a statistically significant d ecrease in the risk of distal forearm fractures (SIR 0.7, 95% CI 0.5-0.97), two of the three sites traditionally associated with osteoporosis. By cont rast, there was a significant increase in subsequent vertebral fractures (S IR 1.9, 95% CI 1.4-2.4) that was consistent across divergent causes of infe rtility and reported menstrual patterns. Although an apparent increase in t he risk of vertebral fractures requires further investigation, we saw no in dication of an increase in limb fractures, suggesting that infertility does not have long-term adverse skeletal effects like those reported for athlet es and dieters with irregular menses.