Oocyte slow freezing using a 0.2–0.3 M sucrose concentration protocol: is it really the time to trash the cryopreservation machine?

Capsule:
We present oocyte slow-freezing outcomes using a differential sucrose concentration during dehydration (0.2 M) and rehydration (0.3 M).

Authors:
Veronica Bianchi, Ph.D., Michela Lappi, B.Sc., Maria Antonietta Bonu, B.Sc., Andrea Borini, M.D.
Volume 97, Issue 5, Pages 1101-1107, May 2012

Objective:
To update results on outcomes with frozen/thawed oocytes using a differential sucrose concentration during dehydration (0.2 M) and rehydration (0.3 M), combined with a one-step propanediol exposure.

Design:
Retrospective cohort study.

Setting:
Private IVF centers.

Patient(s):
Infertile couples undergoing IVF treatment.

Intervention(s):
Oocyte thawing cycles between May 2004 and December 2010.

Main Outcome Measure(s):
Survival, fertilization, and cleavage rates were reported to evaluate biological outcomes. Clinical pregnancy and implantation rates were analyzed as markers of efficiency.

Result(s):
Three hundred forty-two patients and 443 cycles were monitored; the survival was 71.8%, fertilization 77.9%, and of the embryos obtained 83.8% were classified as grade 1 and 2. Three hundred ninety-four transfers were performed, resulting in 90 pregnancies. The pregnancy rate per transfer was 22.8% and per patient was 26.3%, with 122 gestational sacs. The implantation rate per embryo was 13.5%. Patients were divided into three groups according to their age: ≤34 years (group A), 35–38 years (group B), and ≥39 years (group C). Biological outcomes were comparable in all three groups, whereas the pregnancy rate per transfer was higher in the first group (27.7% vs. 21.4% and 17.6%). The implantation rates per injected egg were 11.8%, 8.0%, and 7.5% for the three groups, respectively.

Conclusion(s):
The biological and clinical data obtained on 443 cycles are consistent with our previous results showing that slow freezing of oocytes can be a valid tool in IVF practice when performed with a suitable protocol.

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