This chapter is concerned with research into the effects of exposure to ethylene oxide (EO) on reproductive performance by males and females, on the process and duration of gestation, lactation, and on the survival, growth, and developmental landmarks of the neonatal animal. Evidence of gynecological and obstetric effects of occupational exposure to EO, such as alterations in menstrual cycles and increased incidence of spontaneous abortions, requires careful examination. The chapter examines "gynecological disorders as well as the course of pregnancy and childbirth". The most relevant animal study, involving exposure to EO by inhalation, was conducted by Snellings et al. The rabbit experiment revealed no evidence of maternal toxicity, embryotoxicity, or teratogenicity. Rats do not tolerate exposure to 150 ppm EO very well, and maternal toxicity was particularly manifest in the group having 3 weeks of progestational exposure, followed by 16 days during gestation.