Spontaneous Isthmic Heterotopic Pregnancy Presenting as Suspected Appendicitis With Successful Term Delivery: A Case Report.

Heterotopic pregnancy (HP) is a rare but potentially life-threatening condition defined by the simultaneous presence of intrauterine and extrauterine pregnancies. Spontaneous HPs without identifiable risk factors are particularly uncommon and pose significant diagnostic challenges for clinicians. We report a rare case of a spontaneously conceived isthmic HP in a patient at approximately 11 weeks of gestation who presented with acute abdominal pain. The patient had a confirmed live intrauterine pregnancy (IUP) and no identifiable risk factors for ectopic pregnancy. She was initially evaluated for suspected acute appendicitis and subsequently underwent emergent diagnostic laparoscopy. Intraoperatively, a bleeding isthmic ectopic pregnancy was identified, and a right salpingectomy was performed. The IUP remained viable following surgical management, and the patient ultimately delivered a healthy neonate at 39 weeks' gestation without complications. This case highlights several unusual features, including spontaneous conception in a patient without identifiable risk factors, diagnosis of an isthmic HP at nearly 11 weeks of gestation, and successful term delivery of the IUP following surgical management. It also emphasizes the importance of maintaining clinical suspicion for HP in patients presenting with abdominal pain during early pregnancy, even when a live IUP has already been confirmed.