[Cryopreservation of embryos in the IVF/ET program at the Maternal and Child Care Institute in Prague]

Two methods for embryo cryopreservation using 1,2-propanediol were compared--ultra-rapid vitrification and controlled freezing. No significant differences were found in the pregnancy and implantation rates although better results were achieved by the controlled freezing method. Significantly better results both in pregnancy and implantation rates were obtained when the embryos were frozen in the pronuclear stage compared to cleaved stage embryos. In the group of pronuclear stage embryos 3 pregnancies were achieved as a result of 11 embryo transfers (27%, implantation rate 9%) vs 14 pregnancies from 193 embryo transfers (7%, implantation rate 2.5%) for the cleaved embryos.