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 ovarian hyperstimu lation syndrome (OHSS) (oestradiol greater than or equal to 4500 pg/ml on the day of human chorionic gonadotrophin administration and 25 or more follicles of intermediate or large size) underwent aspiration of all follicles and cryopreservation of all fertilized oocytes at the pr onuclear stage. Patients were monitored for up to 2 weeks post-retriev al, Subsequent transfer of cryopreserved-thawed embryos was performed in programmed cycles using exogenous oestrogen and progesterone for en dometrial preparation, Two patients (13%) developed OHSS necessitating hospitalization and vaginal aspiration of ascitic fluid, Two other pa tients (13%) developed moderate OHSS requiring ascitic fluid vaginal a spiration in the office setting, with dramatic improvement of the cond ition, Subsequent transfer of cryopreserved-thawed embryos yielded a c linical pregnancy rate of 58% per transfer and ongoing or delivery rat es of 42 and 67% per transfer and per patient respectively, By elimina ting pregnancy potential with cryopreservation of all prezygotes and e xamining the pregnancy potential with subsequent cryopreserved-thawed transfers, it is concluded that OHSS is reduced, but not eliminated fo r patients at risk, Subsequent transfer of cryopreserved-thawed prezyg otes in a programmed cycle with exogenous steroids yields an excellent pregnancy rate.