Microinsemination of Human Oocytes

The severely oligozoospermic padent usually has a combination of multiple sperm defects1 with very poor chances of spontaneous conception. In vitro fertilization (IVF) with embryo replacement (ER) has also not improved pregnancies in such cases. De Kretser and co-workers reported that when there is a combination of three or more defects in the semen analysis, fertilization in vitro diminishes to less than 8.0%.2 Even tubal embryo transfer (TET),3 otherwise known as pronuclear stage transfer (PROST) or tubal embryo stage transfer (TEST),4 does not offer hope for such patients as their spouses1 oocytes still need to be fertilized before the transfer of embryos into the fallopian tubes. Zona drilling to assist sperm penetration when first described5 also offered hope for such patients but clinical trials using the technique did not produce any pregnancy.6 Moreover, zona drilling with acid Tyrode’s solution has been found to affect the meiotic process, probably by anaphase II arrest. 7 Recently, Cohen and co-workers described a new approach in which the zona of oocytes were partially dissected using force only via the micromanipulator (partial zona dissection, PZD).8 Using this technique, they have reported three pregnancies,9 which have since increased to six.