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

Area of Science:

• Reproductive Medicine
• Assisted Reproductive Technologies
• Oocyte Cryopreservation

Background:

• Oocyte cryopreservation (OC) is an assisted reproductive technology (ART) option.
• Comparing OC efficiency with conventional in vitro fertilization (IVF) is crucial for patient counseling.
• Live birth per mature oocyte retrieved is a key metric for ART success.

Purpose of the Study:

• To compare the live birth efficiency of oocyte cryopreservation (OC) versus fresh in vitro fertilization (IVF).
• To evaluate live birth rates per mature oocyte retrieved and per embryo transfer (ET).
• To assess the impact of OC on blastocyst formation rates.

Main Methods:

• Retrospective analysis of data from a university-based fertility center.
• Inclusion of 40 women undergoing OC with thaw attempts and 1,908 women undergoing first fresh IVF (2004-2010).
• Separate analysis of autologous and donor-oocyte cycles for women under 40.

Main Results:

• No significant difference in live-birth rate per mature oocyte retrieved (2.7% vs. 4.2%) or live-birth rate per ET (45.8% vs. 51.9%) between OC and fresh IVF.
• OC cycles yielded more oocytes (21 vs. 16), but fewer blastocysts developed (3.9 vs. 6.3).
• A twofold decrease in blastocyst formation was observed in the OC group, independent of age.

Conclusions:

• Oocyte cryopreservation (OC) efficiency is approaching that of fresh IVF regarding live birth rates.
• OC may negatively affect blastocyst development potential.
• Assisted reproductive technology remains an area for efficiency improvements.