A study failing to determine significant benefits from assisted hatching: Patients selected for advanced age, zonal thickness of embryos, and previous failed attempts

Purpose: Pregnancy and implantation rates after mechanical assisted hatching (AH) in patients aged greater than or equal to 38 years, with embryos greater than or equal to 15 mu m in zonal thickness and two or more failed attempts, were assessed at two infertility centers using fresh and frozen embryo transfer (FET) cycles. Methods: AH was performed on 3-day-old embryos. Spare embryos cryopreserved at the two-pronucleus stags were subjected to AH after 2 days of culture and transferred to artificially prepared uteri. Results: In fresh cycles, no significant differences in pregnancy rates (clinical and ongoing) and implantation rates were observed between the AH and the controls for all three selected patient groups (Centers 1 and 2). In FET cycles AH tended to give poor results for greater than or equal to 38 year olds (clinical pregnancy rates of 0 and 5.0% with AH vs 13.3 and 16.7% for controls at Centers I and 2, respectively). With AH, embryos with thick zonae implanted to the same extent as those in the control group and achieved pregnancies for patients with multiple failures (four to six attempts for some) in both fresh and FET cycles. Conclusions: AH failed to show significant benefits in all three patient groups. A larger study group may confirm the effects of AH on frozen/thawed embryos and outcomes for multiple failure cases.