Extracorporeal maturation: Norfolk, 1984.

More than one-half of the laparoscopies undertaken for oocyte retrieval in a program of in vitro fertilization yielded immature (unripened) oocytes. Seventy-three percent of these still possessed an intact germinal vesicle at aspiration. During the period from September 1981 to March 1984, in vitro maturation techniques were applied to the handling of these immature oocytes, with a resulting extracorporeal maturational success reaching 82-85%. The monitoring of germinal vesicle breakdown was essential to determining the fate of the oocytes. No oocytes were successfully fertilized that had normal dipronuclear development unless first polar body extrusion was observed prior to insemination. However, once matured in vitro, these oocytes were fertilized at rates nearly equal to that of mature or preovulatory oocytes. When interval periods of 29 hours between follicular aspiration and oocyte insemination were constant, the incidence of polyspermic fertilization was higher in oocytes that did not possess a germinal vesicle at aspiration compared to that in oocytes with a germinal vesicle. The method of follicular stimulation for ovulation induction was examined to determine whether differences in developmental potential existed between cycles stimulated with hMG alone, FSH alone, or a combination of FSH/hMG. Although fertilization rates were somewhat lower in the combination group, this may have been due to the small number of oocytes involved in that sample. A 50% increase in the number of immature oocytes harvested from FSH cycles was noted. The increasingly higher number of immature oocytes collected for in vitro fertilization underscores the importance of developing reliable in vitro maturation techniques.