Cryopreservation of all prezygotes in patients at risk of severe hyperstimulation does not eliminate the syndrome, but the chances of pregnancy are excellent with subsequent frozen-thaw transfers

In-vitro fertilization patients (n = 15) at risk of ovarianhyperstimulation syndrome (OHSS) (oestradiol > or =4500 pg/ml on the dayof human chorionic gonadotrophin administration and 25 or more follicles ofintermediate or large size) underwent aspiration of all follicles andcryopreservation of all fertilized oocytes at the pronuclear stage.Patients were monitored for up to 2 weeks post- retrieval. Subsequenttransfer of cryopreserved-thawed embryos was performed in programmed cyclesusing exogenous oestrogen and progesterone for endometrial preparation. Twopatients (13%) developed OHSS necessitating hospitalization and vaginalaspiration of ascitic fluid. Two other patients (13%) developed moderateOHSS requiring ascitic fluid vaginal aspiration in the office setting, withdramatic improvement of the condition. Subsequent transfer ofcryopreserved- thawed embryos yielded a clinical pregnancy rate of 58% pertransfer and ongoing or delivery rates of 42 and 67% per transfer and perpatient respectively. By eliminating pregnancy potential withcryopreservation of all prezygotes and examining the pregnancy potentialwith subsequent cryopreserved-thawed transfers, it is concluded that OHSSis reduced, but not eliminated for patients at risk. Subsequent transfer ofcryopreserved-thawed prezygotes in a programmed cycle with exogenoussteroids yields an excellent pregnancy rate.