Soft ultrasound markers of potential fetal aneuploidy
There are several markers of fetal aneuploidy that should be searched for and documented during routine second trimester US.
These are considered “soft” because they are incidental, nonpathologic findings that may be seen in normal fetuses, but are associated with an increased incidence of chromosomal abnormalities, most commonly Down syndrome. The following markers can be used to screen for or adjust the risk for fetal aneuploidies:
- • Increased nuchal thickness (>3 mm first trimester and >6 mm second trimester).
- • Echogenic intracardiac focus.
- • Echogenic bowel.
- • Short long bones (<third percentile for gestational age).
- • Mild renal pyelectasis (anterior-posterior diameter of >4 to 5 mm).
- • Two-vessel cord, single umbilical artery.