Ongoing pregnancies after vitrification of human oocytes using a combined solution of ethylene glycol and dimethyl sulfoxide.

OBJECTIVE: To evaluate a vitrification solution using a mixture of two cryprotectant agents, dimethyl sulfoxide and ethylyne glycol plus sucrose, on the survival of human oocytes. DESIGN: Clinical study of cryopreservation of human metaphase II (MII) oocytes by vitrification. SETTING: University-affiliated IVF center. PATIENT(S): Infertile couples who agreed to have their surplus oocytes vitrified during the fresh IVF cycle. INTERVENTION(S): Vitrification of surplus oocytes subsequently used in the next cycle and assisted fertilization by intracytoplasmic sperm injection. MAIN OUTCOME MEASURE(S): Morphologic survival and normal fertilization, embryo development, and clinical outcome. RESULT(S): A total of 53 surplus MII oocytes from 6 patients were vitrified, of which 24 were thawed, resulting in 18 which survived morphologically (75%). Following insemination, 14 of the 18 surviving eggs were fertilized (77.7%). All zygotes developed into viable embryos that were replaced into each patient's uterus, resulting in two healthy pregnancies: one singleton and one twin. The pregnancies were ongoing. CONCLUSION(S): Cryopreservation of human MII oocytes by vitrification appears to be a promising procedure, though to assure optimal effectiveness of this protocol further studies should be undertaken.