Diagnostic challenges of spontaneous heterotopic pregnancy with concurrent viable intrauterine gestation: a case report.

Heterotopic pregnancy - the simultaneous coexistence of an intrauterine pregnancy and an ectopic pregnancy - is a rare but potentially life-threatening condition. A critical diagnostic pitfall is that the sonographic confirmation of a viable intrauterine pregnancy does not exclude a concurrent ectopic gestation. This report describes the case of a 26-year-old woman who presented at an estimated eight weeks of gestation with haemodynamic instability and free intra-abdominal fluid on focused abdominal sonography. Transvaginal ultrasound confirmed a viable intrauterine pregnancy with no sonographically identifiable adnexal mass, prompting initial conservative management on a working diagnosis of ruptured haemorrhagic corpus luteum. Over the following forty-eight hours, the patient's haemoglobin level fell from 105 g/L to 69 g/L and repeat imaging demonstrated markedly increased pelvic free fluid. Diagnostic and therapeutic laparoscopy confirmed a ruptured left tubal ectopic pregnancy; laparoscopic salpingectomy was performed and the intrauterine pregnancy was preserved. This case underscores that haemodynamic parameters and the trend in serial haemoglobin must guide clinical decision-making even when an intrauterine pregnancy has been confirmed sonographically, and that a low threshold for diagnostic laparoscopy is essential.