Diagnostic Utility of the Sliding Sign in Pregnancy

Definition and Technique

• The American College of Obstetricians and Gynecologists recommends using the sliding sign, which refers to the movement or "sliding" observed between structures during ultrasound examination, particularly with transvaginal ultrasound probe pressure, to differentiate between normal intrauterine pregnancies and ectopic pregnancies 1, 2
• The sliding sign helps determine if a gestational sac or mass moves separately from the ovary, which is important for diagnosing ectopic pregnancies, with a technique involving applying gentle pressure with the transvaginal probe to observe if structures move independently of each other 3, 4

Clinical Significance in Pregnancy

• The sliding sign is particularly valuable in differentiating between tubal ectopic pregnancies and corpus luteum cysts, and can help confirm if an adnexal mass is separate from the ovary, suggesting a tubal ectopic pregnancy 1, 3, 4
• A positive sliding sign helps confirm that a mass or tubal ring moves separately from the ovary, increasing suspicion for ectopic pregnancy 3, 4
• The sliding sign is also useful in diagnosing early pregnancy loss in progress, with movement of a gestational sac, either spontaneously or with uterine pressure from the ultrasound probe, confirming that it is not implanted but transiently located in the lower uterus 5, 6

Differential Diagnosis Applications

• The sliding sign helps differentiate between tubal ectopic pregnancy vs. corpus luteum cyst, early pregnancy loss in progress vs. cervical ectopic pregnancy, and intrauterine pregnancy with eccentric implantation vs. interstitial ectopic pregnancy 1, 4, 5, 6

Diagnostic Accuracy and Limitations

• The sliding sign should be used in conjunction with other ultrasound findings and clinical context, and while highly useful, it should not be the sole criterion for diagnosis 1, 2, 3
• Short-interval follow-up imaging is recommended in indeterminate cases, and the sliding sign is one of several tools to help establish pregnancy location when findings are ambiguous 1, 4, 5

Importance for Patient Outcomes

• Early and accurate diagnosis of ectopic pregnancy is critical as untreated ectopic pregnancies carry significant risk of maternal morbidity and mortality, and proper application of the sliding sign can help avoid diagnostic errors and inappropriate management in pregnancy location assessment 2, 7, 8
• Timely identification of ectopic pregnancies allows for appropriate intervention before rupture occurs, potentially preserving fertility and reducing complications 7