Management of Soft Markers for Down Syndrome
Introduction to Soft Marker Management
- The American College of Obstetricians and Gynecologists recommends that if aneuploidy screening is negative and only an isolated soft marker is present, no further aneuploidy evaluation is needed, with diagnostic testing not recommended solely for isolated soft markers after negative screening 1, 2.
Management Algorithm Based on Screening Status
- For patients with negative screening results and low-risk markers such as echogenic intracardiac focus, choroid plexus cysts, echogenic bowel, urinary tract dilation, or shortened humerus/femur, no further aneuploidy evaluation is required 1, 2, 3, 4, 5.
- For patients with negative screening results and higher-risk markers such as thickened nuchal fold or absent/hypoplastic nasal bone, no further aneuploidy evaluation is needed if cfDNA screening is negative, but counseling regarding residual risk of trisomy 21 and discussion of options including no further testing, cfDNA screening, or diagnostic amniocentesis is recommended if serum screening is negative 1, 2, 4, 5.
Marker-Specific Additional Management
- For echogenic bowel, evaluation for cystic fibrosis, testing for fetal cytomegalovirus (CMV) infection, and third-trimester ultrasound for reassessment and fetal growth evaluation are recommended 2, 4, 5.
- For shortened humerus/femur, evaluation for skeletal dysplasias with thorough measurement of all appendicular bones compared to gestational age nomograms and third-trimester ultrasound for reassessment and growth evaluation are recommended 3, 5, 6.
- For urinary tract dilation, classification as A1 (low risk) versus A2-3 (increased risk) based on anterior-posterior renal pelvis diameter and additional features, and individualized follow-up ultrasound with planned postnatal follow-up are recommended 1, 2, 5.
Critical Pitfalls to Avoid
- Diagnostic testing should not be performed solely for isolated soft markers after negative screening, as this represents a Grade 1B recommendation with strong evidence that the risks of amniocentesis outweigh benefits in this scenario 1, 2.
- Serial ultrasounds to monitor evolution of thickened nuchal fold should not be ordered, as this is not indicated regardless of aneuploidy evaluation pursued 3.
- Fetal echocardiography should not be performed for isolated echogenic intracardiac focus after negative screening, as this is a normal variant 1, 3.
- The presence of multiple soft markers or structural abnormalities changes the approach, with diagnostic testing recommended rather than screening alone 7, 8.