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 cryprotetant agents, dimethyl sulfoxide and ethylyne glycol plus sucrose, on the survival of human oocytes. Design: Clinical study of cryopreservation of human metaphase 11 (MU), 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 11 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.