Objective:

To investigate the association between laser-assisted hatching (LAH) and blastocyst developmental outcomes of day 3 cleavage-stage embryos in fresh IVF cycles.

Approach:

• Study Design: Retrospective analysis of clinical data from 4365 couples who underwent IVF treatment, divided into LAH and non-LAH groups.
• Statistical Methods: Propensity Score Matching (PSM) was used to balance baseline characteristics, followed by Generalized Estimating Equation (GEE) analysis to evaluate the independent effect of LAH.
• Time-Sensitivity Analyses: Sensitivity analyses were performed using ±6-month, ±12-month, and ±24-month time windows to assess potential time-related confounding bias.

Key Findings:

• LAH was associated with a higher transferable blastocyst formation rate, particularly in grade II–IV embryos (P < 0.001).
• No significant improvement in high-quality blastocyst formation was observed.
• Positive associations for transferable blastocyst formation were found in the ±12-month (adjusted rate difference: 4.62%, 95% CI: 1.30%–7.95%, P = 0.006) and ±24-month models (6.69%, 95% CI: 4.46%–8.92%, P < 0.001), but became non-significant after calendar time adjustment (P = 0.573).

Interpretation:

LAH may improve transferable blastocyst formation in low-grade day 3 cleavage-stage embryos under specific analytical conditions, but results were heterogeneous across sensitivity analyses.

Limitations:

• Implantation, pregnancy, live birth, neonatal safety, and long-term offspring outcomes were not assessed.
• Findings should be considered hypothesis-generating and require confirmation in multicenter prospective randomized trials.

Conclusion:

The study indicates that LAH may enhance transferable blastocyst formation under certain conditions.