RESUMO
Numerous studies have repeatedly shown that women who smoke experience problems establishing and maintaining pregnancies, and recent work has further demonstrated that the in utero effects of smoke may not be manifested until months or even years after birth. The purpose of this review is to examine the recent literature dealing with the effects of cigarette smoke on the earliest stages of human prenatal development. Studies in this area have included the use of animal models, patients undergoing in vitro fertilization, and embryonic stem cell models. Events leading to fertilization, such as cumulus expansion, hyperactivation of sperm motility, and oocyte pick-up by the oviduct are all impaired by smoke exposure in animal models. Steps crucial to fertilization such as the acrosome reaction and sperm binding to the zona pellucida are likewise inhibited by cigarette smoke. Preimplantation embryos and stem cells that model embryos show a number of adverse responses to smoke exposure, including poor adhesion to extracellular matrices, diminished survival and proliferation, and increased apoptosis. The current literature demonstrates that the earliest stages of prenatal development are sensitive to smoke exposure and indicates that pregnant women should be advised not to smoke during this time.