Randomized double-blind comparison of laser zona pellucida thinning and breaching in frozen–thawed embryo transfer at the cleavage stage

ObjectiveTo compare the implantation and ongoing pregnancy rates of frozen–thawed embryo transfer (FET) using laser thinning with those of laser breaching of the zona pellucida (ZP).DesignDouble-blind randomized study.SettingA tertiary assisted reproduction unit.Patient(s)Infertile patients undergoing FET cycles.Intervention(s)In the thinning group, more than a quarter of the ZP's outer half-diameter was removed by using a 1,480-nm noncontact laser, whereas a hole about 30 μm in size was created in the ZP in the breaching group.Main Outcome Measure(s)Implantation and ongoing pregnancy rates.Result(s)On the day of the FET, 180 patients were randomly divided into the thinning and breaching groups according to a computer-generated randomization list that was placed in sealed envelopes. The two groups were comparable in terms of demographic characteristics, ovarian response of the stimulated cycle, and quality of fresh and frozen–thawed embryos. The implantation and ongoing pregnancy rates of the thinning group were significantly higher than the corresponding rates of the breaching group but were similar to those of patients without ZP thinning or breaching.Conclusion(s)Laser ZP thinning is associated with significantly higher implantation and ongoing pregnancy rates in FET cycles compared with the case of laser ZP breaching.