Abstract
Ectopic pregnancy accounts for approximately 1%–2% of all pregnancy-related conditions. Among these cases, spontaneous unilateral twin tubal ectopic pregnancy is exceptionally uncommon, with an estimated incidence of approximately 1 in 125,000 spontaneous conceptions. We report a case of a 40-year-old woman with a history of three induced abortions who presented with 7 weeks of amenorrhea, 3 weeks + 2 days of intermittent vaginal spotting, and lower abdominal pain. Serial measurements of serum β-human chorionic gonadotropin (β-hCG) demonstrated a persistent and rapid increase, rising from 11,633.28 mIU/mL to 19,707.09 mIU/mL within four days. Transvaginal ultrasonography revealed two thick-walled cystic structures of increasing size within the left adnexal region, while no gestational sac was identified within the uterine cavity. Histopathological examination following diagnostic curettage showed decidualized endometrium with an Arias–Stella reaction but no chorionic villi. The patient subsequently underwent laparoscopic left salpingectomy. Postoperative pathological evaluation confirmed the presence of two distinct chorionic villous tissue masses, establishing the diagnosis of unilateral twin tubal pregnancy in the left fallopian tube. Our literature review indicated that most previously reported cases were associated with assisted reproductive technologies or identifiable risk factors for tubal damage, whereas spontaneous cases occurring in the absence of recognized predisposing factors remain exceedingly rare. This case highlights that twin ectopic pregnancy should be considered when serum β-hCG levels are disproportionately elevated, and no intrauterine gestational sac is visualized on ultrasonography, even in women with no apparent risk factors. Early recognition through serial ultrasonographic surveillance, in combination with timely surgical intervention, plays a critical role in preventing tubal rupture and optimizing clinical outcomes.