First-trimester presentation of ultrasound findings in trisomy 13 and validation of multiparameter ultrasound-based risk calculation models to detect trisomy 13 in the late first trimester.

The effectiveness of the multiparameter sonographic protocol used for T13 screening showed promising results in patients older than 36 years and suboptimal results in patients between 26 and 36 years old. When screening for T13 left heart defects, CNS anomalies, abdominal anomalies, FHR above the 95th percentile, increased NT, revDV and lack of NB should receive specific attention.