Human pregnancy after transfer of intact frozen-thawed embryos.

Since the birth of the first baby as a result of in vitro fertilisation (IVF) in 1978, many clinics around the world have achieved pregnancies and births for their patients by using IVF and gamete intrafallopian transfer procedures. With the storage of excess embryos, multiple laparoscopies can be avoided; this has favoured the development of better cryopreservation techniques. In our clinic 8-cell human embryos are frozen in a 1.5M dimethyl sulphoxide solution as cryoprotectant using the slow freeze-thaw method. Sixteen thawed embryos were replaced in 8 patients, resulting in 1 pregnancy. Of the thawed embryos 51.6% survived the freezing process in that they had 50% or more of the original number of blastomeres and also the zona pellucida intact.