Selection of Embryos for Day-3 Transfer at the Pronuclear-Stage and Pronuclear-Stage Cryopreservation Results in High Delivery Rates in Fresh and Frozen Cycles1

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Evaluate IVF-ET outcome data for a unique culture and cryopreservation strategy.


Retrospective study of 92 patients. Embryos for day-3 transfer were selected at pronuclear-stage; all extra zygotes were cryopreserved at pronuclear-stage.


Delivery rates for Anonymous Oocyte Donation (Group I), patients <35 years (Group II), and 35–38 years (Group III) were 52.9%, 61.5%, and 51.7% for fresh and 38.5%, 33.3%, and 40.0% for frozen transfer. Deliveries per retrieval were 82.3%, 71.8%, and 58.6%. Only 0.88, 0.80, and 0.61 more zygotes were cultured than what were used for fresh transfer. Singleton, twin, and triplet rates were 64.6%, 31.2%, and 4.2% for fresh and 69.2%, 30.8%, and 0% for frozen.


Selection of day-3 transfer embryos at the pronuclear-stage and cryopreservation of extra zygotes results in high delivery rates in fresh and frozen cycles. This approach optimizes deliveries per retrieval and provides many patients with more than one pregnancy per retrieval.

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