A randomized, prospective study comparing laser assisted hatching and assisted hatching using acidified medium

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Assisted hatching typically involves the mechanical creation of an opening in the zona pellucida (ZP) using an acidified medium (AH) delivered through a micromanipulation pipette. Hatching may also be performed using a 1.48-micron infrared diode laser beam by directing the path of the laser through a 40X objective on an inverted microscope. The objective of this randomized, prospective study was to compare clinical outcomes of patients whose transferred embryos underwent either laser assisted hatching (LAH) or hatching with AM. On the day of embryo transfer (Day 3), consenting patients were randomized according to whether transferred embryos underwent LAH (n=28) or were hatched with AM (n=26). Consenting patients with ≥ 4 embryos at the 7 to 8-cell stage or higher on Day 3 were transferred on Day 5 (n=17) and their results were also analyzed. The results evaluated included the rates of implantation (# fetal heartbeats/# embryos transferred), clinical pregnancy (gestational sac by US) and ongoing pregnancy (≥ 20 weeks). Prior to initiation of this study, approval by the Institutional Review Board and an Investigational Device Exemption from the FDA was obtained. All hatching procedures were performed on the morning of Day 3 at least one hour prior to the scheduled embryo transfer. LAH was performed with the ZILOS-tk laser (Hamilton Thorne Research, Beverly, MA) using a pulse duration of 0.5 msec. Each embryo was positioned so a portion of the zona was in the path of the laser beam. If the hole created did not breach the entire thickness of the ZP, then it was enlarged by applying an additional laser pulse to the adjacent area. Assisted hatching using AM was performed using acidic tyrodes medium (Irvine Scientific, CA) delivered through a glass pipet about 20 microns in diameter (Humagen, CA). Statistical evaluations were performed using an unpaired t-test or chi-square analysis. No significant differences were noted in the mean patient age, number of oocytes aspirated and the number of embryos transferred between the LAH, AM and Day 5 groups. No significant differences were observed in the rates of clinical (54, 50, 74%) or ongoing (43, 35, 63%) between the three groups. In addition, there was no significant difference in the rate of implantation between LAH (32%) and AM (27%) and LAH and Day 5 transfers (50%). However, the implantation rate for AM was significantly lower than that of patients undergoing Day 5 transfers (p=0.0144). These initial findings suggest that the use of a 1.48-micron infrared diode laser beam to perform the assisted hatching procedure does not have a negative impact on patient care when compared to outcomes achieved using acidified medium. The use of a laser to perform assisted hatching allows the operator to perform the procedure quickly and without having to expose the embryos to repeated handling and dish changes. As expected, patients having Day 5 embryo transfers had higher rates of pregnancy and implantation than the two groups that underwent hatching on Day 3. In conclusion, we find that the use of a noncontact diode laser provides safe and rapid method for performing assisted hatching on Day 3.