Table 1.

Definitions of markers used in this study and reported prevalence from previous studies

Marker	Definition	Reported prevalence at fetal anomaly scan from previous studies
Four markers routinely reported in Wales
Echogenic bowel	Areas of increased echogenicity in the fetal bowel as bright as bone. Single or multiple loops of bowel may be identified, and it may be noted to be solid intraluminal echogenicity or occasional echogenicity of the walls only (tram line).	2–14 per 10004, 18, 19
Mild‐to‐moderate ventriculomegaly	Mild‐to‐moderate ventriculomegaly is a ventricular atrial diameter, at any gestation, from 10 to 15 mm. Measurements are obtained from a transventricular axial view at the level of the glomus of the choroid plexus. The callipers were placed on the inner margins of the echogenic ventricular wall.	1 per 100020
Pelvicalyceal dilatation	Fluid filled dilatation of the renal pelvis measured on axial section with an anterior–posterior diameter of 5 mm or greater (callipers to be placed on the inner AP margins of the pelvic wall). This may be unilateral or bilateral.	3–45 per 10004, 17
Thickened nuchal fold	Thickening of the skin and the subcutaneous tissues on the posterior aspect of the fetal neck. This is best viewed in a modified biparietal diameter view to include the cavum septum pellucidum and cerebellum. Assessed by measuring the distance between the skin and occipital bone at the posterior aspect of the neck with the callipers placed on the outer edge of the bone and the outer edge of the skin. A measurement of 6 mm or greater was considered to indicate thickening before 20 + 6 weeks' gestation.	1–6 per 100019, 21, 22
Three additional markers examined in this study
Choroid plexus cysts	Small sonographically discrete fluid‐filled spaces ≥5 mm within the choroid plexus and seen on scan as black echo‐free areas. May be single, multiple, unilateral or bilateral.	6–21 per 100019, 23
Cardiac echogenic foci	Echogenic area on the papillary muscle of either (usually left) or both of the atrioventricular valves	5–49 per 100019, 24, 25
Short femur	Femur length which is below two standard deviations (3rd percentile) for gestational age when measured with the shaft of the femur parallel to the transducer. Care must be taken to ensure that the entire diaphysis of the femur is measured. If the epiphyseal cartilages are visible, they were not included in the measurement. It is assumed that the remainder of the skeleton is normal.	<50 per 10004