Ovarian hyperstimulation syndrome is predicted by HCG serum concentration following the ovulatory dose of HCG

Abstract

Background and Significance: Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication of ovarian stimulation therapy. The severe form is rare, with a reported incidence of 0.5 to 5%. Human chorionic gonadotropin (hCG) is routinely used to induce oocyte maturation and may be a risk factor for development of OHSS. Objective: The purpose of this retrospective study was to evaluate the relationship between serum hCG concentration the day after ovulatory dose of hCG and the subsequent occurrence of OHSS. Materials and Methods: Following ovarian stimulation, hCG was administered via intramuscular injection. Doses varied from 2,500 to 20,000 IU, based on each patient’s weight, age, estradiol concentration, and follicle count. Serum hCG concentrations were measured 12 to 16 hours after injection. Mild OHSS was defined as a constellation of symptoms, including intractable nausea, abdominal distension, vomiting, or diarrhea requiring office visit evaluations. Severe OHSS was defined as a progression of illness accompanied by one or more of the following: tense ascites requiring aspiration, laboratory abnormalities, progressive oliguria, and respiratory difficulty. Logistic regression was used to evaluate the effect of follicle count and hCG serum concentration following the ovulatory dose on the probability of occurrence of OHSS. Results: The study group included 877 IVF cycles that received ovulatory hCG dose between January, 1998 and August, 2003 at a private infertility clinic. Serum concentrations of hCG the day after ovulatory dose ranged from 37 to 731 IU/L, with a mean of 172 IU/L. The study group included 27 cases of OHSS, of which 12 were severe. Follicle count (p<0.0001) and hCG serum concentration (p=0.02) were significant predictors of OHSS (including both mild and severe cases). Similarly, follicle count (p<0.0001) and hCG serum concentration (p=0.05) were significant predictors of severe OHSS. In both models, lack of fit was not significant. Tabled 1[hCG] IU/LEstimated prob(OHSS)Estimated prob(severe OHSS)Follicle countFollicle count15253545152535451000.2%1.6%11.5%50.5%0.1%0.7%4.3%22.6%2000.4%2.7%17.9%63.1%0.2%1.2%7.2%33.7%3000.6%4.5%26.8%74.2%0.3%2.0%11.8%46.9%4001.0%7.3%38.1%82.8%0.5%3.4%18.9%60.6% Open table in a new tab Conclusions: The hCG serum concentration has a dramatic effect on the probability of OHSS and severe OHSS. Patients with low follicle count have relatively low risk of OHSS regardless of hCG level. Clinicians should use restrained hCG dosage, particularly when 25 or more follicles are present.