Systematic review of first-trimester ultrasound screening for detection of fetal structural anomalies and factors that affect screening performance

The recent development of cell-free fetal DNA screening for detection of aneuploidy in the first trimester has shifted the expectations of first-trimester ultrasound examination to detection of structural congenital anomalies and fetal nuchal translucency (NT). Although fetal screening typically occurs in the second trimester, many major structural anomalies can be diagnosed reliably between 11 and 14 weeks' gestation. Varying sensitivity of first-trimester ultrasound and uncertainty about an optimized protocol for its operation have resulted in little consensus about its use in clinical practice