Poor response to gonadotropin stimulation occurs more often in older women but may also be present in young women, including those with normal endocrine profiles as well as those with abnormal endocrine parameters—namely, high baseline FSH and estradiol (E2) levels—known to be associated with poor response. Some poor responders appear to respond to stimulation but have a low estrogen level, whereas others have few or slow-growing follicles. Normally, these patients require prolonged stimulation and higher doses of gonadotropins. They also experience a high cancellation rate because of the smaller number or size of follicles. Many different ovarian stimulation protocols have been tried for treatment of poor responders in IVF. No single protocol seems to benefit all poor respon-ders and treatment continues to challenge those involved in IVF programs (37-39). Although oocyte donation would be the ideal treatment for these patients, some may refuse this option because they would prefer to try using their own oocytes. In these cases, poor responders to previous gonadotropin stimulation may benefit from immature oocyte collection from unstimulated ovaries. In a study by Child et al. (40), eight women with a previous poor response to IVF underwent oocyte collection without ovarian stimulation. hCG was administrated 36 hr before collection. An average of 2.3 immature oocytes were collected and an average of 1.7 matured in vitro. Six of the eight women underwent embryo transfer of 1-3 embryos (average of 1.7); one patient became pregnant and subsequently delivered. The number of embryos produced and available for embryo transfer was similar to that for previous IVF treatments (40). During ovarian stimulation, the small number and size of follicles often warrant cancellation of the cycle. As an alternative to cancellation, immature oocytes could be collected from the stimulated but unresponsive ovaries and then matured in vitro. Such pregnancies were first reported after cryopreservation of in vitro matured oocytes (41). Liu et al. (42) reported eight cases of immature oocyte collection in young patients who had shown poor response to gonadotropin stimulation; three pregnancies were achieved. In another report (43), 41 patients were identified as being resistant to gonadotropin stimulation as the follicles did not grow despite increasing the dosage of gonadotropins. To optimize the successful pregnancy rate among these poor responders, hCG was administered and oocyte retrieval performed 36 hours later because at least some in vivo matured oocytes could be collected after hCG administration. This indicates that immature oocyte retrieval followed by IVM is a possible alternative to cancellation of the treatment cycle in women with poor response following ovarian stimulation (41-43). Based on the results of these preliminary studies, it seems that IVM is a possible option for patients with a poor ovarian response in an ongoing stimulated IVF cycle or with a history of a previous low response to gonadotropin stimulation. Although IVM does not always produce better results than conventional IVF in these cases, it will at least give comparable results without the need for prolonged stimulation with large doses of gonadotropins.
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