Oocyte efficiency: Does live birth rate differ when analyzing cryopreserved and fresh oocytes on a per-oocyte basis?

Objective: To compare the efficiency of oocyte cryopreservation (OC) and IVF using the metric "live births per mature oocyte retrieved." Design: Retrospective analysis. Setting: University-based fertility center. Patient(s): Forty women who underwent OC with thaw attempt between 2004 and 2010; 25 autologous and 15 donor-oocyte treatments were included. One thousand nine hundred eight women underwent their first, fresh conventional IVF treatment between 2004 and 2010; 1,392 used autologous oocytes, and 516 used donor oocytes. Autologous and donor-oocyte cycles were analyzed separately. All oocytes were obtained from women <age 40 years old. Intervention(s): None. Main Outcome Measure(s): Live-birth rate per mature oocyte retrieved (primary outcome), live-birth rate per ET, and blastocyst formation rate. Result(s): When OC/thaw cycles were compared with fresh IVF attempts, there was no significant difference in live-birth rate per mature oocyte retrieved (2.7% vs. 4.2%, respectively) or live-birth rate per ET (45.8% vs. 51.9%). Significantly more oocytes were harvested in the OC versus fresh IVF cycles (21 vs. 16); however, fewer blastocysts developed (3.9 vs. 6.3). Thus, we noted an age-independent approximate twofold decrease in blastocyst formation in the OC group. Conclusion(s): Our data suggest that while assisted reproductive technology remains an inefficient process, OC may be approaching fresh IVF when live birth is the primary consideration. However, OC may negatively impact the potential for blastocyst formation.