Fertility and pregnancy complications were assessed in 137 women at risk of having inherited the gene for autosomal dominant polycystic kidney disease. Seventy-six (55%) of these subjects were found to have polycystic kidney disease (multiple renal cysts). The remaining 61 women served as controls. The prevalence of fertility, spontaneous abortion, stillbirth, and symptoms consistent with urinary tract infection were not different in the two groups. However, the frequency of hypertension first diagnosed during pregnancy (with or without preeclampsia or eclampsia) and the frequency of pregnancy-unrelated hypertension were higher in women with polycystic kidney disease. No evidence was found that pregnancy had an adverse effect on the natural course of polycystic kidney disease. The incidence of renal failure was not higher in women with polycystic kidney disease who had three or more pregnancies than in women of similar ages who had two, one, or no pregnancies.