Objective: To determine the incidence of ovarian hyperstimulation syndrome (OHSS) in a large series of GnRH antagonist-stimulated cycles and to assess the predictive value of E2 and the number of follicles on the day of hCG administration.
Design: Prospective cohort study of women undergoing IVF treatment with a GnRH antagonist protocol over a 2-year period.
Setting: Tertiary university hospital.
Patient(s): One thousand eight hundred one patients who underwent 2,524 cycles.
Intervention(s): Multifollicular ovarian stimulation with recombinant FSH and GnRH antagonist for IVF-ICSI treatment.
Main outcome measure(s): Incidence of OHSS in GnRH antagonist cycles, predictive value of E2, and number of follicles on the day of hCG for OHSS occurrence.
Result(s): Fifty-three patients were hospitalized because of OHSS (2.1%; 95% confidence interval [CI]:1.6-2.8). Early OHSS presented in 31 patients (1.2%; 95% CI: 0.9-1.8), whereas the late type was a complication in 22 patients (0.9%; 95% CI: 0.5-1.3). Late OHSS cases compared with the early OHSS cases always occurred in a pregnancy cycle (100% vs. 40%); had higher probability of being severe (72.7% vs. 42%), and more often were related to a multiple pregnancy (40% vs. 0). Receiver operating characteristic curve analysis for several E2 concentrations and number of follicles with a diameter of > or =11 mm revealed that the predictive value of the optimal threshold of > or =13 follicles (85.5% sensitivity; 69% specificity) was statistically significantly superior to the optimal threshold of 2,560 ng/L for E2 concentrations (53% sensitivity, 77% specificity) in identifying patients at risk for OHSS. Considering that severe OHSS represents the most clinically significant pattern, the combination of a threshold of > or =18 follicles and/or E2 of > or =5,000 ng/L yields a 83% sensitivity rate with a specificity as high as 84% for the severe OHSS cases.
Conclusion(s): Clinically significant OHSS still remains a limitation of multifollicular ovarian stimulation for IVF even with the use of GnRH antagonist protocols. The number of follicles can discriminate the patients who are at risk for developing OHSS, whereas E2 concentrations are less reliable for the purpose of prediction. There is more than ever an urgent need for alternative final oocyte maturation-triggering medication.