Introduction: Delayed diagnosis of tubal pregnancy may cause intra-abdominal hemorrhage secondary to tubal rupture or tubal abortion and progress to a shock state. Recent advances in transvaginal ultrasound devices and simplified measurement of blood hCG levels have made it possible to perform early pregnancy diagnosis before the onset of symptoms and to provide early treatment. We describe a patient with an ampullary tubal pregnancy in whom the fetus grew until week 11 of gestation without resulting in either rupture or miscarriage. This patient could be treated with laparoscopic surgery. Case presentation: The patient was a 37-year-old woman, gravida 0, para 0. Pregnancy had been achieved using artificial insemination at a nearby clinic. She received a diagnosis of pregnancy with uterine malformation and was referred to our hospital at 10 weeks and 5 days of gestation. The blood hCG level was 154,243.8 IU/L. A pregnancy in the left rudimentary uterine horn of the right unicorn uterus was suspected based on ultrasound and MRI examination. At 11 weeks and 1 day of gestation, she underwent laparoscopic surgery under general anesthesia. She had a small amount of hemorrhagic ascites and the uterus was normal in size without findings of uterine malformation; accordingly, pregnancy in the rudimentary uterine horn and abdominal pregnancy were both ruled out as possibilities. The fimbria