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

BACKGROUND: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: Once oolema penetration during ICSI has proven difficult, prospective hatching of embryos considered for transfer may increase their implantation behaviour.