Importance of prenatal ultrasound in the early diagnosis of TRAPs and analysis of missed and misdiagnosed cases

This study aimed to evaluate the diagnostic value of ultrasonography performed at 12 to 14 weeks of gestation for twin reversed arterial perfusion sequence (TRAPs) and analyze the causes of missed diagnoses and misdiagnoses during this gestational period. Six cases of TRAPs diagnosed during the first trimester at the Department of Ultrasound, First Affiliated Hospital of Shandong First Medical University, between January 2015 and September 2022 were retrospectively analyzed. The ultrasound features, TRAPs classifications, and causes of early misdiagnosis were summarized. Five of the 6 cases were diagnosed at 12 to 15 weeks of gestation, and all involved monochorionic diamniotic twin pregnancies. Among them, 4 cases were classified as holoacardius acephalus, 1 as acardiac amorphous, and 1 as acardiac acranial. Among the acardiac twins, 3 had generalized edema and 2 had cystic hygroma. Among the pump twins, 1 had ascites, and another had multiple choroid plexus cysts and tetralogy of Fallot. No additional abnormalities were detected in the remaining acardiac twins. Color Doppler imaging showed reversed umbilical arterial flow entering the abdominal cavity through the umbilical region of the acardiac twins. Prenatal ultrasound in the first trimester can help diagnose TRAPs early. In addition, understanding the disease and the Color Doppler observation of the characteristic reverse umbilical blood flow is key to early diagnosis and avoiding misdiagnosis of such cases.