Maturation of immature oocytes by coculture with granulosa cells.

To increase the number of embryos available for transfer, immature human oocytes were cocultured with granulosa cells from preovulatory follicles. Greater numbers of immature oocytes incubated with granulosa cells had dispersion of the cumulus and corona cells compared with immature oocytes cultured in media alone. Fifty-four percent of immature oocytes were fertilized after coculture with granulosa cells compared with 20% fertilization of immature oocytes cultured without granulosa cells. There were no cases in which only embryos developed from immature oocytes were transferred, and thus we could not determine if the immature oocytes could contribute to a pregnancy.