Assisted hatching by zona drilling of human embryos in women of advanced age

The study was conducted to examine the efficacy of the zona drilling technique for promotion of successful implantation and pregnancy by assisting embryo hatching in women of advanced age undergoing treatment by in-vitro fertilization. A total of 839 embryos from 211 patients aged > 38 years underwent assisted hatching during 312 cycles of therapy. The outcome of this micromanipulation procedure was compared to 540 non-hatched pre-embryos transferred to 174 patients during 274 cycles of therapy. Assisted hatching was performed on four- to eight-cell stage embryos using the zona drilling technique. In the assisted hatching group, 839 micromanipulated embryos were replaced (two to four embryos per patient) compared to 540 embryos transferred in the control group. Despite the fact that the pregnancy rate was not statistically different between the groups (8.9% in the assisted hatching group versus 5.1% in the controls) a trend towards an increase was noted in the assisted hatching group. The implantation rate was 3.75 and 3.55% per patient respectively, and there was no significant difference in abortion rate between the groups. The delivery rate was 3.8 and 3.4% per cycle respectively. The results of this study demonstrated that assisted hatching by zona drilling in a selected group of patients aged > 38 years does not increase the take-home baby rate after in-vitro fertilization treatment.