Adverse pregnancy outcome from environmental factors may include congenital anomalies, increased risk for miscarriage, preterm delivery, intrauterine growth restriction, and still birth. Apart from adverse pregnancy outcome, there may be effects on the other reproductive functions, like menstrual disorders and infertility. Environmental factors which have been implicated in adverse pregnancy outcome include smoking, video display terminals, anesthetic gases, antineoplastic drugs, and exposure to lead, selenium, and inorganic mercury. Among these, cigarette smoking during pregnancy has been the leading environmental factor for adverse pregnancy outcome. Cigarette smoking during pregnancy continues to be a significant public health concern. Maternal smoking during pregnancy has been associated with low birth weight (<2500 g). Mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants. Similarly, air pollution, pesticide exposure, and stress have also been associated with low birth weight and preterm delivery. This review gives an overview of the importance of environmental factors in adverse pregnancy outcome. © 2007 Elsevier Inc. All rights reserved.