Background: Ovarian hyperstimulation syndrome (OHSS) is almost exclusively associated with ovulation induction with gonadotropins or occasionally, clomiphene citrate. Severe ovarian hyperstimulation associated with a spontaneously conceived pregnancy is rare with only two previous reports. Misdiagnosis as a neoplastic process may result in inappropriate intervention. Case: A patient with polycystic ovarian disease experienced severe spontaneous OHSS in four consecutive singleton pregnancies. Serial color and pulsed Doppler ultrasonographic imaging facilitated adequate evaluation of the patient and permitted conservative therapy. She achieved live births in two of the pregnancies. This is the third reported case of spontaneous OHSS associated with pregnancy and the first to result in live births. In one previous report, misdiagnosis resulted in inadvertent castration. Conclusions: Spontaneous ovarian hyperstimulation syndrome and pregnancy may occur in patients with polycystic ovarian disease. Color Doppler ultrasonography is a useful aid in the diagnosis and management of this rare complication, and in avoiding inappropriate intervention.