Laser assisted thinning versus drilling in cryopreserved embryo transfer cycles

ABSTRACT
Objective. Human embryo cryopreservation is a crucial aspect of Assisted Reproduction (AR). Nonetheless there is a potential concern regarding zonal hardening, which may have a negative impact on AR outcome. Assisted hatching (AH) has been employed to facilitate microdissection of the zona pellucida. Both laser assisted thinning and drilling techniques have been used to address this issue. However insufficient studies compared laser thinning versus opening technique. We aimed to study the effect of laser assisted hatching on cryopreserved embryos, comparing both laser assisted thinning and laser assisted drilling techniques and their effects on both implantation rate chemical and clinical pregnancies.
Patients and Methods. 300 women were randomized into 3 equal groups (thinning, drilling and control group) and prepared for transfer of frozen/thawed embryos. The thinning and opening techniques were performed on the day of embryo transfer while the zona of the control group was left intact.
Results. Both the chemical and clinical pregnancy rates were higher in laser-thinning group over the control group in all women enrolled in the study (P-value = 0.04, 0.031, respectively) and specifically above age of 35 years old P-value = 0.003, 0.006, respectively) with a significant implantation rate (P-value 0.043) on addition. However, laser-drilling group showed no advantage over neither the control group or the thinning group.
Conclusions. Laser thinning technique for cryopreserved embryos increased both the chemical and clinical pregnancy rates in frozen embryo transfer especially above age of 35 years old and it seems to have the upper hand in relation to laser opening technique.