The widespread use of sonographic markers, such as echogenic intracardiac focus (EIF) or choroid plexus cyst (CPC) to assist in identifying fetuses at increased risk for common aneuploidies (trisomy 21, 18, 13) dates back to the 1980s. However, since the more recent introduction of earlier and more sensitive aneuploidy screening methods such as cell-free DNA testing (aka noninvasive prenatal screening, NIPS) and first trimester nuchal translucency screening algorithms (such as Sequential screening), it has been unclear how best to counsel patients when an isolated sonographic marker for aneuploidy is identified on the fetal anatomy survey. In an attempt to help with this clinical challenge, SMFM has recently published recommendations to address this common scenario.
To briefly summarize, in the setting of either a prior low-risk NIPT, first trimester screen, Sequential screen, or Quad screen:
- the presence of a single sonographic marker for aneuploidy on a detailed fetal anatomic survey will be considered a normal variant (with comments to that effect on the report). These include echogenic intracardiac focus, choroid plexus cyst, sandal toe gap and clinodactyly.
- the presence of two or more sonographic markers associated with aneuploidy should prompt additional individualized genetic counseling with diagnostic testing presented as an option.
- isolated sonographic markers that have additional clinical significance should be evaluated based upon the individual finding, but will not be commented upon as an aneuploidy marker. These include pyelectasis, two-vessel umbilical cord (a.k.a., single umbilical artery), ventriculomegaly, echogenic bowel, thick nuchal fold, hypoplastic nasal bone, and shortened femur or humerus.
In the absence of prior low-risk results, the management and counseling of patients for identified sonographic markers for aneuploidy should continue as before, with additional counseling, individualized risk assessment, and offering either screening (via NIPT or second trimester serum screening) or diagnostic testing via amniocentesis.
If you have any questions regarding this change in management recommendations, please do not hesitate to reach out to any of the MFM specialists or genetic counselors at NWP.