THE EFFECT OF ASSISTED HATCHING ON PREGNANCY RATES AFTER FROZEN EMBRYO-TRANSFER

Objective: To compare clinical pregnancy and implantation rates after transfer of frozen-thawed embryos prepared according to an assisted ha tching protocol or a nonassisted hatching protocol. Design: A historic al cohort study in which a cohort of patients who underwent an assiste d hatching protocol was matched for clinical parameters to an external historical cohort treated before assisted hatching was available. Set ting: In vitro fertilization-ET facility of a university-based practic e. Patients: Seventy-nine matched pairs. Interventions: Nonassisted ha tching patients: embryos were thawed, cultured in human tubal fluid 0.5% bovine serum albumin until 48 hours and transferred. Assisted hat ching patients: embryos thawed, cultured in human tubal fluid + 10% sy nthetic serum substitute until 72 hours, had assisted hatching and tra nsferred. Main Outcome Measures: Clinical pregnancy (gestational sac) and implantation rates. Results: Twelve (15.2%) clinical pregnancies p er transfer in nonhatched group versus 24 (30.4%) in hatched group. No nhatched group: 284 embryos transferred; 15 (5.3%) implanted. Three pr egnancies (25.0%) had two sacs. Hatched embryos: 269 were transferred; 37 (13.7%) implanted. Eleven pregnancies (45.8%) were multiple gestat ions (9 twins, 2 triplets). Conclusion: Clinical pregnancy and implant ation rates were higher for group having assisted hatching protocol. I t is not clear whether the improvement is due to the overall methodolo gy change or to assisted hatching. Assisted hatching using the zona-dr illing technique is not detrimental to frozen-thawed human embryos and may be beneficial.