Use of a zona laser treatment system in assisted hatching: optimal laser utilization parameters.

Objective: This study aimed to establish the benefit of laser micromanipulation of the zona pellucida as a method of assisted hatching and to determine the optimal technical settings.

Design: Prospective pilot study.

Setting: University teaching hospital.

Animal(s): Six- to 8-week-old F1 female mice.

Intervention(s): Mouse embryos were treated with a laser (Hamilton Thorne Research) using both research and preset clinical settings. The research option allows the user to alter pulse duration, number of pulses, and beam intensity. In this study, laser intensity and duration, as well as the depth and number of disruptions, were altered.

Main Outcome Measure(s): Embryos were scored after treatment as either arrested blastocysts, arrested during hatching, hatched, or degenerate.

Result(s): The treatment where the laser intensity was halved but the number of laser pulses used was doubled was the most beneficial treatment. Zona thinning was not effective.

Conclusion(s): The study showed that laser-assisted hatching can safely and significantly increase the percentage of embryos reaching the hatched blastocyst stage. A proportionately sized hole in a human embryo may have the same beneficial effect as has been shown in this study.