OBJECTIVE: To evaluate the implantation rate achieved after chemical removal of the zona pellucida from day 5 human in vitro-derived embryos. DESIGN: Prospective, randomized, controlled study. SETTING: A tertiary care infertility clinic. PATIENT(S): Two hundred fifty-seven patients undergoing IVF with transfer of morulas or blastocysts on day 5 after oocyte retrieval. All patients had had at least two previous implantation failures. INTERVENTION(S): Chemical removal of zona pellucida by using acidic Tyrode's solution vs. no removal (controls). MAIN OUTCOME MEASURES: Clinical pregnancy rate and implantation rate per transfer. RESULT(S): Embryos without zona pellucida implanted at nearly twice the rate of control embryos (15.7% vs. 27.5%). The pregnancy rate was also significantly higher in the zona pellucida-free group than the control group (31.0% vs. 46.1%). Removal of zona pellucida was most effective in embryos with delayed development, which reached the morula or early cavitating stage on day 5 of in vitro culture (implantation rate, 12.1% vs. 25.7%). CONCLUSION(S): Chemical removal of zona pellucida from day 5 in vitro cultured human embryos is an effective and safe method of significantly improving the implantation rate, especially of embryos with delayed development.
RCT Entities:
OBJECTIVE: To evaluate the implantation rate achieved after chemical removal of the zona pellucida from day 5 human in vitro-derived embryos. DESIGN: Prospective, randomized, controlled study. SETTING: A tertiary care infertility clinic. PATIENT(S): Two hundred fifty-seven patients undergoing IVF with transfer of morulas or blastocysts on day 5 after oocyte retrieval. All patients had had at least two previous implantation failures. INTERVENTION(S): Chemical removal of zona pellucida by using acidic Tyrode's solution vs. no removal (controls). MAIN OUTCOME MEASURES: Clinical pregnancy rate and implantation rate per transfer. RESULT(S): Embryos without zona pellucida implanted at nearly twice the rate of control embryos (15.7% vs. 27.5%). The pregnancy rate was also significantly higher in the zona pellucida-free group than the control group (31.0% vs. 46.1%). Removal of zona pellucida was most effective in embryos with delayed development, which reached the morula or early cavitating stage on day 5 of in vitro culture (implantation rate, 12.1% vs. 25.7%). CONCLUSION(S): Chemical removal of zona pellucida from day 5 in vitro cultured human embryos is an effective and safe method of significantly improving the implantation rate, especially of embryos with delayed development.