title: Human preimplantation embryo cryopreservation: selected aspects.
abstract: This report describes the results of cryopreserving human preimplantation zygotes and cleaved embryos (2-4 cells) in our in-vitro fertilization programme. Cryopreserved zygotes and cleaved embryos resulted in similar post-thaw survival rates (74.8 versus 70.9%). Pregnancy rates per retrieval cycle (RC) and embryos transferred per pregnancy for frozen-thawed zygotes versus frozen-thawed cleaved embryos were 21.8 versus 11.5% (P less than 0.2) and 12.6 versus 17.5 (P less than 0.2), respectively. Pregnancy rates increased significantly for both fresh (P less than 0.0005) and frozen-thawed (P less than 0.05) embryos as the number of embryos replaced per transfer increased from one to three or more. Frozen-thawed embryos resulted in multiple implantation rates per transfer of 25 compared to 6.4% (P less than 0.1) for fresh embryos when two embryos were replaced. Pregnancy rates were reduced for fresh (P less than 0.05) and frozen-thawed (P less than 0.1) embryos obtained from patient retrieval cycle numbers greater than 3. The method of follicular stimulation during the retrieval cycle did not affect frozen-thawed embryo survival rates. There was no difference in pregnancy rates from frozen-thawed embryos replaced during natural or clomiphene citrate transfer cycles. Patients with cryopreserved embryos had cumulative pregnancy rates of 37.1% (66/178) compared to 23.5% (110/468) (P less than 0.01) for patients with no embryos cryopreserved; cryopreservation of preimplantation embryos is a reliable therapeutic procedure that enhances achievement of pregnancy through in-vitro fertilization.
authors.affiliation: Genetics & IVF Institute, Fairfax, VA 22031.
authors.forename: E F
authors.initials: EF
authors.lastname: Fugger
authors.forename: M
authors.initials: M
authors.lastname: Bustillo
authors.forename: A D
authors.initials: AD
authors.lastname: Dorfmann
authors.forename: J D
authors.initials: JD
authors.lastname: Schulman
mesh_terms: D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation / Q000009:adverse effects / Q000379:methods*; D010064:Embryo Implantation; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy