The cryopreservation of embryos in late developing stages seems to present satisfactory results. With the purpose of better testing the embryos' survival, they were cryopreserved in the morula or blastocyst stage, thawed and left in culture for 24 hours so that their natural evolution could be observed. Amongst the frozen 2 blastocysts and 5 morulas, 4 morulas survived the thawing process, being transferred as blastocysts 24 hours later. The transfer was performed in a young patient, second marriage of a ten-year vasectomized man and resulted in twin pregnancy. Thawing morula embryos and the in vitro observation of their development resumption until the blastocyst stage give us an additional parameter in the quality evaluation of the embryo and probably an improvement in pregnancy rates.
Infertility; "In vitro" fertilization; Embryo cryopreservation