[Comparison of various methods of cryopreservation of human pre-embryos].

A human egg and embryo freezing program for non-fertilized eggs and spare embryos has been established in our in vitro fertilization clinic. In the following we report on our first experience with different methods of human pre-embryo cryopreservation. In a simple evaluation we have compared different conventional freezing techniques using cryoprotectant substances such as glycerol, DMSO and 1.2 propanediol and an "ultrarapid" technique. So far we have achieved 6 normal ongoing and 2 biochemical pregnancies out of a total number of 61 embryo transfers. This equals 9.8% pregnancy rate per embryo transfer. Two methods seem preferable, i.e. sucrose and 1.2 propandiol which has the highest success rate and the ultrarapid method which gives a good rate of embryo survival on the one hand and a simple handling on the other.