Evidence suggests that shiftwork is associated with menstrual irregularities, reproductive disturbances, risk of adverse pregnancy outcome, and sleep disturbances in women, yet little has been done to evaluate the effects of shiftwork on menstrual function and fertility. The purpose of this study was to evaluate menstrual function, fertility, and pregnancy outcome in nurses working shiftwork, and to examine the relationship of sleep to menstrual function. Sixty-eight nurses < 40 years old completed a survey evaluating sleep, menstrual function, and pregnancy outcome. Fifty-three percent of the women noted menstrual changes when working shiftwork. Women noting menstrual changes reported more physiological symptoms (p < 0.003), slept approximately one hour less when working nights, and reported lengthened time to fall asleep (p < 0.01) when working nights. Findings suggest that sleep disturbances may lead to menstrual irregularities, and changes in menstrual function may be a marker of shiftwork intolerance.