Spontaneous Conception During Ovarian Stimulation Complicated by Severe Ovarian Hyperstimulation Syndrome (OHSS) With Atypical β-Human Chorionic Gonadotropin (β-hCG) Trends: A Case Report.

Ovarian hyperstimulation syndrome (OHSS) is a known complication of ovarian stimulation and may complicate the interpretation of β-human chorionic gonadotropin (β-hCG) in early pregnancy. Importantly, pregnancy can still occur during ovarian stimulation, and in this setting, ectopic pregnancy must be carefully excluded, given the potential for tubal dysfunction related to fluid shifts, increasing diagnostic uncertainty. We present a 28-year-old woman who developed severe OHSS following controlled ovarian stimulation, in whom spontaneous conception occurred prior to planned intrauterine insemination. Serial β-hCG levels showed an initial plateau, likely reflecting fluid shifts and residual exogenous hCG, followed by a delayed rise, raising concern for abnormal pregnancy. However, early ultrasound confirmed a viable intrauterine pregnancy, and the patient subsequently delivered a healthy infant. This case highlights the limitations of relying solely on β-hCG trends in OHSS and underscores the importance of integrating clinical findings and early ultrasound to guide management.