Genetic evaluation of the fetus with soft markers for aneuploidy on ultrasound examination before serum or cell-free DNA screening

CVS: chorionic villus sampling; FISH: fluorescence in situ hybridization.
* For invasive testing, CVS is offered through 14 weeks of gestation; amniocentesis is offered at 15 weeks of gestation and beyond.
¶ FISH may be performed but is often omitted to save time.
Δ A positive cell-free DNA screening test must be confirmed with a diagnostic test, particularly if pregnancy termination is planned based on test results.
◊ A FISH test panel should include chromosomes 13, 18, 21, X, and Y. Although FISH provides a rapid result, it also adds to the cost of the fetal evaluation, so it is also reasonable to proceed directly to chromosomal microarray.
§ Some soft markers (eg, echogenic bowel, single umbilical artery, urinary tract dilation, shortened long bones) are associated with disorders other than aneuploidy, which may require additional evaluation, including diagnostic testing. Refer to UpToDate content on prenatal genetic evaluation of the fetus with anomalies or soft markers for recommendations regarding further evaluation of pregnancies with these markers.