2 ESSENTIAL STEPS FOR A SUCCESSFUL INTRACYTOPLASMIC SPERM INJECTION -INJECTION OF IMMOBILIZED SPERMATOZOA AFTER RUPTURE OF THE OOLEMA

A total of 740 cycles of intracytoplasmic sperm injection (ICSI) were performed: 625 cycles when <6x10(5) total motile spermatozoa were harv estable from the ejaculate and 115 cycles in cases with a history of p revious fertilization failure after classic in-vitro fertilization or subzonal sperm injection. An average of two pronuclei were observed in 63% of the injected oocytes, allowing 725 transfers of a maximum of t hree embryos (98%). Of 214 pregnancies initiated, 179 were established (25% of ICSI attempts). Because the fertilization rates from our init ial 80 ICSI cycles were 2-fold less than those achieved previously, we changed the injection procedure and analysed, in 740 ICSI attempts, t he importance of interfering technical factors and how to establish a successful ICSI programme. A remarkable change in the fertilization ra te up to 68% (595 cycles) occurred when two steps in the injection pro cedure were performed well, i.e. immobilization of the spermatozoon an d placement of the spermatozoon into the ooplasm after cytoplasmic asp iration into the pipette until oolema rupture. This immobilization, by touching the tail with the pipette, is mandatory for increasing the p ercentage of fertilization, even with totally non-motile spermatozoa ( 41%). Because aspiration of the cytoplasm is an invasive part of the I CSI procedure and influences the quality of the embryos, it is essenti al to reduce the amount of cytoplasm drawn into the pipette. This coul d be attained by using a spikeless injection pipette with the smallest possible internal diameter.