Clinical Benefits and Safety Profile of Laser-Assisted Zona Thinning in Frozen Cleavage-Stage Embryo Transfers: Evidence from 940 ICSI/FET Cycles

Laser-assisted zona thinning (LAZT) has been proposed to enhance embryo implantation by facilitating zona pellucida (ZP) hatching. This retrospective study evaluates the impact of LAZT on clinical and neonatal outcomes in vitrified-warmed cleavage-stage embryo transfers. A total of 940 patients undergoing ICSI/FET between September 2021 and February 2025 were analyzed. Patients were divided into two groups: 574 underwent LAZT, and 366 served as controls. Subgroup analyses were performed based on age (< 35 and ≥ 35 years) and infertility etiology. The LAZT group exhibited significantly higher biochemical pregnancy (40.1% vs. 29.5%), clinical pregnancy (24% vs. 14.75%), implantation (10.4% vs. 5.75%), and live birth rates (23.3% vs. 14%) compared to controls (P < 0.05). No significant differences were observed in neonatal outcomes such as preterm birth, infant sex, or the presence of congenital malformations. Notably, women aged ≥ 35 years showed more pronounced benefits in biochemical and live birth rates. Patients with polycystic ovary syndrome and multiple infertility factors also demonstrated improved outcomes. However, increased pregnancy complications (11.19% vs 3.92%, P < 0.01) were observed in the LAZT group, necessitating cautious clinical application.