The existence of a motility-inhibiting substance in human peritoneal f
luid (hPF) has been demonstrated. The results of this study indicate t
hat this factor from hPF is a heat-resistant, volatile molecule with a
very small molecular mass (e.g., halothane, which is used for general
anesthesia in laparoscopic GIFT). This may be the reason for the conf
licting results concerning pregnancy rates in gamete intrafallopian tr
ansfer.