Zona-intact versus zona-free blastocyst transfer: a prospective,randomized study

OBJECTIVE: To compare the outcome of zona-intact versus zona-free blastocyst transfer. DESIGN: Prospective, randomized study. SETTING: Tertiary care private hospital IVF center. PATIENT(S): A total of 240 patients undergoing blastocyst stage ET (119 zona intact and 121 zona free). INTERVENTION(S): In vitro culture of embryos to the blastocyst stage was followed by random allocation to zona-intact or zona-free transfer. MAIN OUTCOME MEASURE(S): Treatment cycle characteristics, implantation, and pregnancy rates. RESULT(S): Transfer of zona-free blastocysts was associated with a higher implantation rate. Subgroup analysis, however, indicated that better outcome was achieved only in the group that received poor-quality blastocysts. Patients undergoing blastocyst transfer for the first time did not seem to benefit from zona-free blastocyst transfer. CONCLUSION(S): Zona-free blastocyst transfer increases the success of blastocyst-stage transfer in patients with poor-quality blastocysts.