OUTCOME OF THAW EMBRYO-TRANSFER AFTER CRYOPRESERVATION OF ALL EMBRYOSIN PATIENTS AT RISK OF OVARIAN HYPERSTIMULATION SYNDROME

Objective: To determine the incidence of ovarian hyperstimulation synd rome (OHSS) and subsequent pregnancy rates (PRs) if ET is delayed in p atients at risk of OHSS by allocating all embryos to cryopreservation. Design: Retrospective analysis of clinical and laboratory data from 7 24 consecutive stimulated cycles of IVF. Setting: University hospital- based IVF program. Patients: Consecutive patients undergoing IVF betwe en September 1989 and December 1992. Main Outcome Measures: Fertilizat ion rates, cryosurvival rates, subsequent PRs, and the occurrence of s evere OHSS. Results: Ten of the 564 patients (1.8%) who had ET in the stimulation cycle developed severe OHSS. Sixty-nine patients had all e mbryos frozen because of the risk of OHSS, of which one (1.4%) develop ed severe OHSS. The subsequent PR after thaw transfer was 25.2% per tr ansfer, with a cumulative PR per patient after additional thaw transfe rs of 40.6%. Conclusions: Cryopreservation of all embryos and delayed ET in patients at risk of OHSS results in a low incidence of severe OH SS. Oocyte quality, fertilization rates, and cryosurvival of frozen em bryos are equal to those for patients who have a normal stimulation pr ofile. Subsequent thaw embryo replacements result in a satisfactory PR .