In Vitro Fertilization Outcomes Following Assisted Hatching of Embryos with Thick Zona Pellucida—A Prospective Randomized Study

Abstract

Purpose: Impaired hatching is associated with implantation failure following in vitro fertilization (IVF). Thickening or hardening of the zona pellucida (ZP) has been proposed as a factor in this impairment. We examined whether selective assisted hatching (AH) is beneficial with embryos having a thick ZP. Methods: This prospective, randomized controlled study was performed in the IVF unit of an obstetrics and gynecology department in a university-affiliated hospital. Only pa-tients undergoing IVF and having a ZP thickness of ≥17 µm measured in all their embryos were in-cluded. In the intervention group, AH was applied to all embryos, before their transfer. In the con-trol group, embryos were transferred without AH. Implantation, clinical pregnancy and live birth rates were the study endpoints. Results: Both study arms were comparable in most baseline pa-rameters. The two groups did not differ in implantation rates (14.1% control vs. 8.92% interven-tion, odds ratio (OR) = 0.5974, 95% confidence interval (CI) 0.325 -1.1), clinical pregnancy rates (36.7% vs. 25.8%, OR = 0.6025, 95% CI 0.274 -1.325), or live birth rates (25% vs. 18.9%, OR = 0.7021, 95% CI 0.291 -1.691). Conclusions: Selecting embryos for AH by their ZP thickness as a sole parameter was not found to be beneficial and to improve IVF outcome. Keywords In Vitro Fertilization, Assisted Hatching, Zona Pellucida Thickness, Partial Zona Dissection, Implantation Rate M. Koifman et al.