Outcome of thaw embryo transfer after cryopreservation of all embryos in patients at risk of ovarian hyperstimulation syndrome

To determine the incidence of ovarian hyperstimulation syndrome (OHSS) and subsequent pregnancy rates (PRs) if ET is delayed in patients at risk of OHSS by allocating all embryos to cryopreservation. Retrospective analysis of clinical and laboratory data from 724 consecutive stimulated cycles of IVF. University hospital-based IVF program. Consecutive patients undergoing IVF between September 1989 and December 1992. Fertilization rates, cryosurvival rates, subsequent PRs, and the occurrence of severe OHSS. Ten of the 564 patients (1.8%) who had ET in the stimulation cycle developed severe OHSS. Sixty-nine patients had all embryos frozen because of the risk of OHSS, of which one (1.4%) developed severe OHSS. The subsequent PR after thaw transfer was 25.2% per transfer, with a cumulative PR per patient after additional thaw transfers of 40.6%. Cryopreservation of all embryos and delayed ET in patients at risk of OHSS results in a low incidence of severe OHSS. Oocyte quality, fertilization rates, and cryosurvival of frozen embryos are equal to those for patients who have a normal stimulation profile. Subsequent thaw embryo replacements result in a satisfactory PR.