Prospective hatching of embryos developed from oocytes exhibiting difficult oolemma penetration during ICSI

The hormonal milieu during ovarian stimulation is known to affect oolemma behaviour as well as zona pellucida thickness and structure. This led us to investigate whether a special subgroup of patients with oocytes where penetration of the oolemma is difficult during ICSI may benefit from assisted hatching.

A total of 77 couples (mean age: 32.9 +/- 4.6 years; range: 22-38) had oocytes that could hardly be penetrated by the ICSI pipette. Nineteen patients underwent two ICSI cycles, giving a total number of 96 cycles, which were randomly split into either the study group (n = 52) or the non-hatching group (n = 44). Hatching was done using a non-contact 1.48 mm wavelength diode laser. Implantation and pregnancy rates were recorded.

The pregnancy rate was 36.6% (19/52) in the study group and 13.6% (6/44) in the non-hatching group (P < 0.05). In addition, a higher number (P < 0.05) of embryos implanted in the study group (23/106; 21.7%) than in the non-hatching group (9/92; 9.8%).

Once oolema penetration during ICSI has proven difficult, prospective hatching of embryos considered for transfer may increase their implantation behaviour.