The prevalence of lumbosacral intervertebral disk bulge and herniation on sagittal magnetic resonance (MR) images was determined in 45 pregnant subjects and 41 asymptomatic nonpregnant women of childbearing age. MR technique differed for the pregnant and nonpregnant groups. Fifty-three percent of pregnant and 54% of nonpregnant women had an abnormal disk (bulge or herniation) at one or more levels (L3-4, L4-5, or L5-S1). The difference was not statistically significant. There was also no significant difference in the distribution of outcomes among the 45 pregnant subjects, 17 parous nonpregnant women, and 24 nulliparous women. The results suggest that lumbosacral disk bulges or herniations are common in women of childbearing age, whether pregnant or not, and that, contrary to an earlier report, pregnant women do not have an increased prevalence of disk abnormalities.