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

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.Retrospective cohort study.Private IVF centers.Infertile couples undergoing IVF treatment.Oocyte thawing cycles between May 2004 and December 2010.Survival, fertilization, and cleavage rates were reported to evaluate biological outcomes. Clinical pregnancy and implantation rates were analyzed as markers of efficiency.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.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.