TRISOMY 21 second-trimester ultrasound

The second trimester is an ideal time to perform a thorough ultrasound eval uation of a fetus. Numerous ultrasound markers in the head, chest, abdomen, and extremities are used to access the risk of a fetus for trisomy 21 and other types of aneuploidy. Finding any structural cardiac abnormality or an abnormally thickened nuchal skin fold should lead to consideration of a ka ryotype analysis. Other findings should be used in both low- and high-risk populations to adjust the risk of aneuploidy and individualize prenatal cou nseling.