Utilizing a 20-plane systematic ultrasound protocol to detect fetal structural abnormalities during the first trimester

Objective Most first-trimester prenatal ultrasound studies and reviews to date described observations of fetal anatomical structures; however, explicit standard sectional images or standardized ultrasound examination protocols are lacking. This study aimed to ascertain the efficacy of systematic ultrasound screening for fetal structural abnormalities. Method This retrospective analysis examined the results of first-trimester systematic ultrasound screenings performed of 30,336 fetuses between June 2019 to and 2022 and compared them with second- and third-trimester ultrasound screening, postpartum examination, and post-mortem examination results. Results Among the 30,336 fetuses, 4.1% (1,240) had structural abnormalities, of which 37.1% (460/1,240) were severe. Overall, 32.2% (399/1,240) of the structural abnormalities were detected via the systematic ultrasound screening, among which 79.7% (318/399) were severe. Of the 318 fetuses with severe abnormalities, 69.1% (220) featured nuchal translucency (NT); 21.1% (220/1,240) of the fetuses with structural abnormalities presented with increased NT versus 46.1% of those with severe structural abnormalities. Of the structural abnormalities detected by the systematic ultrasound screening, 54.6% featured increased NT. Systematic ultrasound screening had a sensitivity of 32.2% and specificity of 99.82% for the identification of fetal structural abnormalities. Areas by sensitivity level were as follows: ≥80%, anterior abdominal wall abnormalities, syndromes, edema/coelomic hydrops; 50–80%, nervous system structural abnormalities; 30–50%, other abnormalities and limb and skeleton structural abnormalities; and < 30%, congenital heart defects and facial, gastrointestinal tract, urogenital system, and thoracic and lung-related structural abnormalities. Combined screening exhibited higher sensitivity than systematic ultrasound screening alone (P < 0.001). Conclusion Systematic ultrasound screening detected most serious fetal structural abnormalities; however, its efficacy varied significantly among systems and diseases. Increased NT may be an important indicator of serious structural abnormalities. Furthermore, combined screening of fetal structural abnormalities has higher efficacy.