Local experience with zona drilling, zona cutting and sperm microinjection

Abstract

Clinical trials were performed between 1987 and 1992 on the use of zona drilling (ZD), zona cutting (ZC) and subzonal sperm microinjection (SZI) for the treatment of severe male infertility. ZD significantly improved the fertilization rate, but embryo morphology was poor and no pregnancies were achieved, so it was abandoned in favour of ZC. The fertilization rate was acceptable in the first trial of ZC but embryo morphology was still poor and no pregnancies were achieved, so a number of protocol changes were instigated. Shrinkage of oocytes in hypertonic sucrose prior to ZC markedly improved embryo quality, whereas transfer of embryos on Day 3 after oocyte retrieval enhanced the pregnancy rate. 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 cycles 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 successful treatment for severe male infertility; under the trial conditions, at least, it was superior to ZD or ZC.