Imaging in gynecological disease (32): clinical and ultrasound characteristics of early abdominal ectopic pregnancy.

objectivesTo compare clinical and sonographic characteristics of first-trimester abdominal ectopic pregnancy (AEP) with those of tubal ectopic pregnancy (TEP), and to define ultrasound-based diagnostic criteria for AEP.

methodsThis was a retrospective case-control study comparing cases of AEP diagnosed at four centers with controls diagnosed with TEP, between May 2008 and May 2025. AEP was defined as a pregnancy implanted within the peritoneal cavity outside the uterus, ovaries and Fallopian tubes. We compared demographics, clinical and ultrasound findings and clinical outcomes between the groups. We identified the key ultrasound features of first-trimester AEP and used these to develop refined diagnostic criteria.

resultsDuring the study period, 19 cases of AEP were identified and compared to 57 controls with TEP. The groups were matched for age, parity and gestational age at presentation. Compared with TEP, AEP was more likely to occur in pregnancies conceived via in-vitro fertilization (6/19 (32%) vs 5/57 (9%); odds ratio (OR) 4.80 (95% CI, 1.27-18.21); P = 0.02; adjusted OR (aOR), 5.02 (95% CI, 1.24-20.25); P = 0.02) and patients with AEP were less likely to present with vaginal bleeding (5/18 (28%) vs 40/57 (70%); OR, 0.16 (95% CI, 0.05-0.53); P = 0.003; aOR, 0.17 (95% CI, 0.05-0.64); P = 0.009). With respect to clinical outcomes, patients with AEP were more likely to have significant blood loss (≥ 500 ml) at surgery (4/16 (25%) vs 1/36 (3%); OR, 11.67 (95% CI, 1.18-114.90); P = 0.04) and require blood transfusion (4/19 (21%) vs 0/56 (0%); P = 0.003). Four diagnostic ultrasound criteria for AEP were identified: (1) the presence of a gestational sac or trophoblast separate from the uterus and ovaries; (2) the absence of a hypoechogenic tissue layer surrounding the pregnancy; (3) a negative 'sliding organs' sign; and (4) trophoblastic blood flow arising from the peritoneum detected on color Doppler examination.

conclusionsAssisted conception is a risk factor for a pregnancy implanting into the peritoneal cavity. Early ultrasound diagnosis of AEP is important to reduce the risk of major intra-abdominal bleeding, which is significantly higher in AEP compared with TEP. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.