LOCAL EXPERIENCE WITH ZONA DRILLING, ZONA CUTTING AND SPERM MICROINJECTION

Clinical trials were performed between 1987 and 1992 on the use of zon a drilling (ZD), zona cutting (ZC) and subzonal sperm microinjection ( SZI) for the treatment of severe male infertility. ZD significantly im proved the fertilization rate, but embryo morphology was poor and no p regnancies were achieved, so it was abandoned in favour of ZC. The fer tilization rate was acceptable in the first trial of ZC but embryo mor phology was still poor and no pregnancies were achieved, so a number o f protocol changes were instigated. Shrinkage of oocytes in hypertonic sucrose prior to ZC markedly improved embryo quality, whereas transfe r of embryos on Day 3 after oocyte retrieval enhanced the pregnancy ra te. However, despite these improvements, the overall pregnancy rate in the third ZC trial was still low (16.6% per transfer), so a trial of SZI was initiated in 1992. The overall fertilization rate in 82 SZI cy cles was 34.4% and, although the polyspermy rate was high, a clinical pregnancy rate of 30.8% per transfer and an implantation rate of 18.4% per embryo were achieved. These trials demonstrate that SZI is a succ essful treatment for severe male infertility; under the trial conditio ns, at least, it was superior to ZD or ZC.