Objectives

To develop and validate a nomogram based on fetal nuchal translucency (NT) and ultrasonographic facial markers for the screening of trisomy 21 in the first-trimester of pregnancy.

Methods

This was a retrospective case-control study using stored 2D midsagittal fetal profile images captured at 11+0 to 13+6 weeks’ gestation. Our database was used to identify 302 cases of trisomy 21 pregnancies and 322 euploid pregnancies. For each case, the maternal age and ultrasonographic facial markers were investigated. Least absolute shrinkage and selection operator (LASSO) method and multivariable analysis were used to select the discriminative markers automatically. Logistic regression was used to develop a model (LASSO-model) based on the selected markers to screen for trisomy 21 in the first-trimester of pregnancy. Furthermore, 60 cases were randomly selected as a retest set to evaluate the model’s robustness. The predictive performance of the model of fetal NT and maternal age, the model of all markers of this study and the LASSO-model for the screening of trisomy 21 was assessed using area under receiver operating characteristic (ROC) curve (AUC). A nomogram was developed as an individualized tool to predict patient-specific probability for trisomy 21, which is a more intuitive presentation of the LASSO-model. The performance of the nomogram was assessed using C-index and calibration curve.