Oviductal function is critical for very early human life

For normal fertilization, the ovum must be picked up from the ovarian surface or from the abdominal cavity into the ampulla. The rapid transport of gametes includes a complex reorganization of the oviductal smooth muscle electrical activity that precedes the mechanical activity. The 3-day stay at the ampulla-isthmic junction requires both signals from the ovum to the oviduct and vice versa, supporting the ovum and regulating its to-and-fro movements. Oviductal fluid, a principal factor in tubal function, coats the newly fertilized egg, activates transcription and gives a signal for sperm fertility potential. Early blocks to embryo development in in vitro conditions, as compared to in vivo success, means that critical developments during the first cell cycles of embryonic life in the oviduct are actively regulated by oviductal embryotrophic factors. These have been used clinically in co-culture systems. Lytic factors are weak in human and other primates, predisposing to high incidence of tubal pregnancies, with considerable impact on medical practice. Diverse oviductal factors affect the incidence, infection being the most significant. Optimal oviductal function is necessary to provide a proper environment for early human life.