Effect of laser assisted hatching (LAH) on fresh blastocysts and clinical outcomes

Abstract

The purpose of this study was to evaluate the clinical outcomes of LAH performed on fresh-day 5 blastocysts prior to transfer. This was a retrospective matched case-control study which included patients who underwent a fresh-day 5 blastocyst transfer between May 2013 and April 2014 at the MUHC Reproductive Centre. Patients undergoing fresh stimulated cycles as well as in-vitro maturation cycles were included in this study. Blastocysts were collapsed first using the laser then had LAH performed on the same side as the inner cell mass. Approximately 5-8 laser pulses were delivered in order to completely rupture the zona pellucida (ZP) along roughly ¼ of its diameter. Early stage blastocysts did not undergo shrinking prior to LAH but an opening in the zona was created via 2-3 laser pulses ensuring that the inner ZP layer had been breached. A control group was generated from fresh day 5 blastocyst transfer cycles that did not undergo LAH. Characteristic differences among the groups were analyzed using Z-test or Student’s t-test and outcomes were compared using chi-square test and Fisher’s exact test when appropriate. A P-value <0.05 was considered significant. A total of 208 cycles were included in the study, 104 in each group. The two groups were comparable in that there were no significant differences in age, serum FSH level, antral follicle count, stimulation protocol or cause of infertility. Additionally, the number of oocytes collected and fertilized as well as the number of embryos transferred and implanted did not differ. The overall pregnancy rate and clinical pregnancy with fetal cardiac activity in the LAH group were 56.73% and 40.38% and in the control group were 49.04% and 36.54% respectively. Among women over 40 years old, the implantation rate was 28.57% in the LAH group compared to 8.33% in the control group (p<0.05). Similarly, the rate of pregnancy with fetal cardiac activity was higher in the study group than in the control group (32.14% vs. 8.33%, p<0.05). Women over 40 years old have a decreased pregnancy rate. Assisted hatching of fresh blastocysts can benefit older patients who traditionally have lower chances of success.