Literature review and suggested protocol for managing ultrasound soft markers for Down syndrome: thickened nuchal fold, echogenic bowel, shortened femur, shortened humerus, pyelectasis and absent or hypoplastic nasal bone.

Mid-trimester soft markers have been linked with Down syndrome and other aneuploidies. There are many other prenatal screening tests available with better detection rates for Down syndrome than the mid-trimester ultrasound. Many patients confronted with the diagnosis of a soft marker become anxious and may request a diagnostic test (amniocentesis) despite the associated risk of miscarriage. This is also despite the fact that most fetuses with an isolated soft marker are chromosomally normal. The management of a pregnancy with a soft marker must therefore be planned in a manner designed to minimize patient anxiety. Likelihood ratios can be used to modify a patient's 'prior risk' (based on age or prior screening tests) and create a new risk. This calculation may help identify a subset of patients suitable for further investigation. It has been proposed that 'negative' likelihood ratios can be used to reduce a patient's risk if no soft marker is found at a mid-trimester ultrasound. There remain concerns about this approach and further research is required before this approach enters common practice. The published work surrounding the management of thickened nuchal fold, echogenic bowel, shortened femur, shortened humerus, pyelectasis (renal pelvis dilatation) and hypoplastic nasal bone is reviewed. Each soft marker has different associations and individual management plans for each of these soft markers are presented. Although isolated single umbilical artery is not usually considered a soft marker of aneuploidy, a management plan for this common finding is also included.