Pregnancies after transfer of ultrarapidly frozen human embryos.

Abstract

We report our experience of freezing human embryos using an ultrarapid freezing method. The patients were superovulated. Oocytes were inseminated and cultured in HTF + 10% serum. A maximum of three embryos was transferred and the rest of the embryos were frozen ultrarapidly after a 3-min equilibration period in PB1 + 3.5 M DMSO + 0.25 M sucrose. Embryos were thawed in a 37 degrees C water bath for 6 sec, then cultured in PB1 + 20% serum for 10 min. The surviving embryos were transferred into patients on the same day of thawing. Sixty-three embryos were thawed, of which 52 embryos (83%) survived with at least one intact blastomere. Nineteen frozen-thawed embryo transfers were made. The mean embryos per transfer was 2.7. Three pregnancies (16%/transfer) were established. One miscarriage occurred in the eighth week of pregnancy. Two pregnancies went to term and three healthy infants were born. The present data demonstrate that ultrarapid freezing is a method worth consideration in the area of human embryo freezing.