Clinical pregnancy and live births after transfer of embryos vitrified on day 3.

Human embryo vitrification is a promising new technology but clinical outcome data is needed to gauge its effectiveness and safety. While pregnancy and live-birth data is available for blastocyst vitrification, such information is lacking for human embryo vitrification at the 6- to 8-cell stage. The current work presents clinical and obstetric outcomes from the transfer of embryos vitrified on day 3 at the cleavage stage. A total of 270 transfers were performed. The clinical pregnancy and implantation rates for patients under 38 years of age (n=200) were 45% and 24%, respectively. Corresponding rates in patients 38-42 years old declined to 29% and 13% (n=70). Embryonic compaction and/or blastulation by the time of transfer were excellent prognostic indicators of a successful pregnancy outcome. Of the 66 deliveries, 12 (18.2%) were twin pregnancies and nine were preterm (13.6%). The mean birthweight for singletons was 3281+/-644 g, compared with 2506+/-549 g in the twin pregnancies. A total of 78 infants have been born with no major congenital malformations. These data attest to the efficacy and safety of the vitrification technique for cryopreservation of human embryos at the 6- to 8-cell stage.