Abstract
OBJECTIVE: To describe a rare case of ovarian hyperstimulation syndrome (OHSS) presenting as an isolated right-sided pleural effusion because of endogenous human chorionic gonadotropin (hCG) production from a naturally conceived pregnancy during a luteal-phase ovarian stimulation cycle. DESIGN: Single-patient case report with longitudinal follow up. SUBJECT: A healthy 36-year-old woman with a 15-month history of primary infertility who was undergoing her second luteal-phase ovarian stimulation cycle. EXPOSURE: Controlled ovarian stimulation with menotropins, recombinant follicle-stimulating hormone, letrozole and somatropin, followed by endogenous hCG production from an unexpected naturally conceived pregnancy; no exogenous hCG trigger was administered. MAIN OUTCOME MEASURES: Onset and clinical course of OHSS; volume and recurrence of pleural effusion; need for thoracentesis or an indwelling pleural catheter; maternal and neonatal outcome. RESULTS: A total of 17 ovarian follicles developed by stimulation day 11 with a modest peak estradiol concentration of 279 pg/mL, underscoring the unexpected nature of the subsequent severe presentation. Serum hCG measured 53 mIU/mL on day 11 and rose to 231 mIU/mL 2 days later, confirming conception and prompting cancelation of the stimulation cycle. After 6 days, the patient developed worsening dyspnea; imaging revealed a large right pleural effusion. Three thoracenteses over 10 days removed 4,700 mL of fluid before placement of a 12-French indwelling pleural catheter, which promptly relieved symptoms. Bilateral ovarian enlargement was present with no evidence of ascites. The pregnancy then progressed uneventfully until preterm delivery of a healthy infant at 32 weeks of gestation; both mother and child were discharged in good condition. CONCLUSION: Ovarian hyperstimulation syndrome can occur despite low estradiol concentrations and the absence of an exogenous hCG trigger. Endogenous hCG from an unrecognized early pregnancy can independently provoke severe vascular hyperpermeability even in canceled cycles with low estradiol and no trigger shot. Clinicians should maintain vigilance for respiratory complications and perform routine pregnancy testing during luteal-phase stimulation to avert delayed diagnosis and morbidity.