Successful pregnancies from cryopreserved human embryos produced by in vitro fertilization.

Sixty-three embryos produced after in vitro fertilization in 30 infertile couples were frozen and stored. Dimethylsulfoxide was used as a cryoprotectant and embryos were frozen from the two-cell stage to early blastocyst development. Replacement occurred during spontaneous ovulatory cycles 2 to 15 months after embryo freezing. Embryo replacement was performed 3 to 6 days following identification of the luteinizing hormone surge in the spontaneous cycle. Thirty-five embryos were replaced into 25 women and two viable pregnancies resulted.