Pregnancy, ciliary transport, and the reversed ampullary segment of the rabbit fallopian tube.

Pregnancy following reversal of an ampullary segment in the rabbit oviduct has occurred only sporadically, and then usually after repeated mating. To explain this phenomenon it has been postulated that the direction of ciliary beat in the reversed ampullary segment must revert to the normal pro-uterine direction. To test this hypothesis a segment of the ampulla was reversed by microsurgery in 10 rabbits. These were then bred repeatedly for as long as 28 weeks. A single pregnancy, at 10 weeks, ensued. Observation of ampullary transport in vivo showed that muscular activity in the reversed ampullary segment may occasionally overcome the adverse, pro-ovarian ciliary currents that were found to persist in subsequent in vitro examinations. Scanning electron microscopy confirmed normal ciliation in the reversed segment. These observations may explain the occasional transport of an ovum across the reversed ampullary segment and an isolated pregnancy in the mated rabbit.