Aims: To compare the screening capability of ultrasonography in detecting trisomy 13 (T13) using a multiparameter sonographic protocol (NT+) with a classical combined screening test (CST) protocol.
Methods: The project was a prospective, multicenter study based on a nonselected mixed-risk population of women referred for a first-trimester screening examination. Each subject was offered a choice between either the gold standard, traditional combined screening test (CSG arm) or the ultrasound-based screening protocol (USG arm).