Subzonal sperm microinjection in cases of severe male factor infertility and repeated in vitro fertilization failure

To examine (1) fertilization rates obtained with subzonal sperm microinjection when different numbers of sperm are injected into the perivitelline space; (2) when subzonal sperm microinjection is combined with dilute insemination; and (3) the association of semen quality characteristics with fertilization.

Subzonal sperm microinjection and subzonal sperm microinjection combined with dilute insemination was performed in 109 and 41 cycles on patients in two clinical trials in Melbourne, Australia, and Bologna, Italy, respectively. PATIENT PARTICIPANTS: Couples who have experienced repeated in vitro fertilization failure or in whom the husband has severe male factor infertility.

The number of oocytes fertilized after injection of different numbers of sperm into the perivitelline space, the number of patients transferred, and pregnancy outcome.

The injection of multiple numbers of sperm into the perivitelline space failed to improve monospermic fertilization rates but caused an increase in polyspermic fertilization. In patients with initial semen parameters exhibiting greater than 50% motility or greater than 50% normal morphology fertilization rates were improved when subzonal sperm microinjection-treated eggs were incubated in a dilute insemination medium. Six pregnancies were obtained, two of which have progressed to term.

When applied to male factor patients, the subzonal sperm microinjection technique results in a 14% to 15% fertilization rate. However, of the 102 embryos transferred only three (2.9%) fetal heart beats were obtained.