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A 27-year-old woman was admitted to the obstetric emergency department for abdominal pain without bleeding at 8 weeks’ gestation. She had a previous uneventful pregnancy delivered vaginally at term, and an early scan performed 2 weeks before the symptoms occurred revealed an ongoing intrauterine pregnancy.

The patient underwent transvaginal sonography (MyLab 25; Esaote SpA, Florence, Italy), which showed an intrauterine pregnancy with a live embryo measuring 29 mm, consistent with a gestational age of 8 weeks 5 days. A second gestational sac with irregular and undefined boundaries containing an active embryo measuring 17 mm was depicted in the rectouterine pouch (Figure 1). Both ovaries were visualized as normal, and no pelvic free fluid collection was noticed during the scan. These findings were consistent with a diagnosis of heterotopic pregnancy.

Heterotopic pregnancy refers to the rare occurrence of both intrauterine and ectopic pregnancies usually located in one fallopian tube, cervix, or, more rarely, abdomen. Assisted reproduction techniques, tubal surgery, pelvic inflammatory disease, and the use of intrauterine devices represent the most common risk factors.1

Sonography is the mainstay for diagnosis of heterotopic pregnancy, allowing for the detection of two gestational sacs located inside and outside the uterus, respectively, and blood collection in the pelvis. In addition, clinical symptoms such as pain and genital tract bleeding can help in achieving the diagnosis.1

In this case, the patient had no risk factors for this condition, with a previous uneventful pregnancy delivered at term and no history of pelvic surgery or disease. To confirm the diagnosis, the woman was asked to fill her bladder, and transabdominal sonography was performed. Interestingly, only the intrauterine gestational sac was found, with a normal appearance of the rectouterine pouch and no ectopic pregnancy detected.