Early and late presentation of the ovarian hyperstimulation syndrome: two distinct entities with different risk factors.

This study was designed to identify clinical predictors for early and late ovarian hyperstimulation syndrome (OHSS). A retrospective analysis of all 592 in-vitro fertilization (IVF) cycles from the programme's inception in 1988 up to March 1993 was performed. Six patients (1.0% of cycles) had moderate or severe OHSS presenting 3-7 days post-human chorionic gonadotrophin (HCG), and four patients (0.7% of cycles) had severe OHSS presenting 12-17 days post-HCG. No patient with early OHSS went on to develop late OHSS, and no patient with late OHSS had demonstrated early OHSS. Stepwise logistic regression showed that early OHSS was predicted by the number of oocytes retrieved (range 18-46) (P = 0.0001) and the oestradiol concentration on the day HCG was given (range 12,122-24,454 pmol/l) (P = 0.0003). Late OHSS was predicted by the number of gestational sacs (range 2-3) on ultrasound 4 weeks after embryo transfer (P = 0.0001) but not by the number of oocytes or oestradiol. Early OHSS was an acute effect of the HCG administered prior to egg retrieval in women with high oestradiol and larger numbers of follicles (range 22-51). Late OHSS was induced by the rising serum concentration of HCG produced by the early pregnancy, and in this series of cases it was associated only with multiple gestation.