Received May 03, 1997
Accepted June 17, 1997

Introduction:Our objective was to study the frequency of human immature oocytes and the probability of maturation and fertilization in vitro, under ICSI procedures.A prospective analysis was carried, where the oocytes number in prophase(PI), metaphase I(MI) and metaphase II(MII) were studied, in order to establish correlation among the in vitro maturation percentage, comparative MII fertilization and percentage and the impact on number of embryos to transfer. Materials and Methods:During a nine months period, one hundred ICSI cycles were analyzed in which ejaculated sperm was injected.The oocytes were classified after being treated with hyaluronidase and the immature ones were cultivated in HTF media with 1 5% patient's serum.Observations were carried on every 4 hours interval, during the first 24 hours from aspiration, with micromanipulation of those which extruded the first polar body.Fertilization and cleavage rates were checked on days:+1 and +2, respectively. Results:We classified 1339oocytes and found 1120MII(83.6%).ln 60cases we had immature oocytes, as follows:121PI(9.1%) and 98MI(7.3%).The fertilization and cleavage rate for the MIIoocytes were 67.4% and 86.5% respectively.The maturation, fertilization and cleavage rate for MIoocytes were 71. 4%, 52.5% and 62. 4% respectively and, statistically different(p<0.05) from the PIoocytes(46.3%, 31.1% and 42.8% respectively). At day +2, we had 45 embryos derived from immature oocytes. Conclusions:Immature oocytes were found in 60% of the cases, showing no correlation with any clinical parameter of the patients.The higher the immaturity grade, the lower the probability of fecundation and division.In principle, the immature oocytes fertilization is possible, as an additional gain in the final embryos number.