Rescue of implantation potential in embryos with poor prognosis by assisted zona hatching

The effect of the assisted zona hatching (AZH) procedure was investigatedon 135 cycles with a poor prognosis of pregnancy due to: (i) maternal age> or = 38 years (45 cycles); (ii) three or more failed in-vitrofertilization (IVF) attempts (70 cycles), and (iii) patients possessingboth inclusion criteria (20 cycles). The control groups (113 cycles)included patients possessing the same characteristics (42, 53 and 18 cyclesrespectively) and who did not undergo the AZH procedure. A total of 505embryos was treated with AZH before transfer, resulting in: 14, 25 and 6clinical pregnancies. The percentage of clinical pregnancies per cycle wassignificantly higher than controls for the first (31 vs 10% in control 1, P< 0.05) and second groups (36 vs 17% in control 2, P < 0.05). Nosignificant difference in percentage of clinical pregnancies was found forthe third group (30 vs 6%). Similarly, higher rates of implantation wereobtained (11.5, 15 and 11%) compared to the respective controls (4%, P <0.02; 6.3%, P < 0.01; and 1.5%). The rate of miscarriage in the AZHgroups was similar to that obtained in the controls (22 vs 21%). Finally,the morphological analysis of the embryos transferred revealed that thepoor prognosis condition is associated to a significantly slower rate ofdevelopment and a higher rate of fragmentation. The present resultsindicate that AZH procedure improves pregnancy and implantation rates inpatients with a poor prognosis of pregnancy by facilitating the hatchingprocess in embryos which would otherwise be trapped inside the zonapellucida.