The Utility of the Ultrasound “Superimposed-Line” Sign at the Junction of the Vomer and Maxilla in First-Trimester Screening for Fetal Cleft Palate: A Case-Control Study

Abstract

Introduction: The current retrospective case-control study evaluates the diagnostic value of screening for a fetal cleft palate by using the ultra-sound-based observation of the “superimposed-line” sign appearing at the junction of the vomer and maxilla in the first trimester of pregnancy. Methods: Retrospective analyses were performed of ultrasonographic images of nuchal translucency obtained during the first trimester of pregnancy (11–13⁺⁶ weeks) from 45 fetuses with a cleft palate later confirmed following parturition or induced labor (cases) and 4,500 normal fetuses confirmed after parturition (controls). Ultrasonographic features of the “superimposed-line” sign were observed and recorded, and between-group comparisons were performed. Results: The “superimposed-line” sign was absent in 39 cases (86.67%), including 4 (8.89%) with simple secondary hard palate cleft and 35 (77.78%) with secondary hard palate cleft complicated by a primary cleft palate. The “superimposed-line” sign was shown in 6 cases (13.33%), including 2 (4.44%) with a simple secondary soft palate cleft, 1 (2.22%) with a simple secondary bifid uvula, and 3 (6.67%) with a simple primary cleft palate. Among the 4,500 controls, 31 fetuses showed an absence of the “superimposed-line” sign (0.69%) and 4,469 showed the “superimposed-line” sign (99.31%). The between-group difference was significant (p < 0.05). The sensitivity, specificity, positive predictive value, and negative predictive values of the “superimposed-line” sign in the first trimester of pregnancy for predicting fetal cleft palate were 86.67% (39/45), 99.31% (4,469/4,500), 55.71% (39/70), and 99.86% (4,469/4,475), respectively. Conclusion: The “superimposed-line” sign did not appear in fetuses with secondary hard palate cleft and primary cleft palate only when a secondary hard palate cleft is present. The sign appeared in normal fetuses and those with a simple primary cleft palate, simple secondary soft palate cleft, or a simple secondary bifid uvula. Based on these results, we propose that the “superimposed-line” sign in the mid-sagittal plane of the fetal face in the first trimester of pregnancy (11–13⁺⁶ weeks) is an important tool in screening for fetal cleft palate, especially secondary hard palate cleft.