The use of ovulation-inducing agents in in-vitro fertilization.

In view of the increasing pregnancy rate associated with increased numbers of embryos transferred to the uterus, it is optimal to transfer more than one embryo to each patient. This requires treatment with ovulation-inducing agents to increase the number of preovulatory follicles developing. However, the degree of ovarian "hyperstimulation" must be limited to prevent subsequent luteal-phase dysfunction. In all probability, the ideal regimen for enhanced follicular recruitment to achieve these goals has not as yet been determined. Up to this time multiple different regimens have been used throughout the world, all of which have achieved an increase in the number of embryos available for uterine replacement. Unfortunately, as the degree of augmented follicular development is increased, there appears to be a progressive shortening of the luteal length. It remains to be determined whether or not this shortening of the luteal length can be overcome by pharmacologic support of the luteal phase. In addition, if all embryos recovered are to be transferred to the uterus in the treatment cycle, there is a substantial risk (ranging from 10% to 35%) that if a woman becomes pregnant, she will have a multiple pregnancy. As ethical constraints challenge the advisability of selecting only some of the available embryos for uterine replacement, the development of cryopreservation for subsequent uterine replacement appears highly desirable.