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.

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