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At 22 days after intrauterine insemination with ovulation induction using clomiphene citrate at a previous hospital, a 30-year-old woman was admitted to our hospital owing to right lower quadrant abdominal pain. We diagnosed threatened abortion because of a gestational sac in the uterus on transvaginal ultrasonography. The next day, she complained of increased abdominal pain. Transvaginal ultrasonography revealed a gestational sac-like structure in the echo free space. She was diagnosed with heterotopic pregnancy due to a ruptured right tubal pregnancy, underwent laparoscopic right salpingectomy. Rupture of a gestational age of 5 weeks is extremely rare. If this was a case of a heterotopic pregnancy due to superfetation, it could be explained as this clinical course. When a pregnant woman develops abdominal pain, heterotopic pregnancies should not be excluded from the differential diagnosis, and the possibility of superfetation should be taken into consideration.