Risk factors for ovarian hyperstimulation syndrome in Thai patients using gonadotropins for in vitro fertilization

Purpose. A prospective observational study was conducted to identify risk factors for ovarian hyperstimulation syndrome (OHSS) in Thai patients using gonadotropins for in vitro fertilization. Methods. Outpatients receiving a short and a long protocol of ovarian stimulation with a recombinant follicle-stimulating hormone (rec FSH) at a Bangkok hospital were enrolled. Patients in the short protocol received rec FSH and the gonadotropin-releasing-hormone agonist buserelin acetate by subcutaneous injection after blood sampling on day 2 of the patient's cycle. When one or more follicles reached a diameter of 18 mm as determined by ultrasonography and the serum estradiol (E-2) concentration exceeded 400 pg/mL, patients received human chorionic gonadotropin (hCG); oocytes were retrieved 34-36 hours later. The long protocol differed only in that patients received nasal buserelin acetate and rec FSH 10 days before the cycle started and on day 2 of the cycle. Serum levels of E-2' luteinizing hormone, and FSH were monitored at baseline. In addition to E-2 concentration and follicle size and number, patients' weight, waist circumference, complete blood counts, and C-reactive protein (CRP) levels were monitored at intervals. Patients were instructed to notify the hospital of any symptoms of OHSS. Results. Of 117 patients enrolled, 13 had moderate OHSS and 1 had severe OHSS; all recovered. Patients with OHSS were significantly younger, had significantly lower body mass index, and had significantly higher E-2 before hCG injection, total number of follicles, total number of oocytes retrieved, and white blood cell and neutrophil counts after hCG injection. Patients with polycystic ovary syndrome were significantly more likely to have OHSS. CRP levels were higher in OHSS patients, but the difference was not significant. Multiple logistic regression showed that the combination of serum E-2 peak concentration of >= 4500 pg/mL and total number of oocytes retrieved of >= 15 predicted the occurrence of moderate-to-severe OHSS; 12 of 14 study patients who met these criteria had OHSS. Conclusion. Serum E-2 peak concentrations of >= 4500 pg/mL and total number of oocytes >= 15 may be useful indicators for identifying patients at high risk for moderate-to-severe OHSS.