Ultrasonographic “soft markers” of fetal chromosomal defects

Detecting them may do more harm than good

Most women in Britain have at least one ultrasound scan during their pregnancy. Aside from confirming viability and establishing gestational age, ultrasound may also indicate the possibility of an abnormality. An obvious structural problem, such as anencephaly, will have predictable consequences that can be discussed with the patient with some confidence. Less straightforward is the case in which a scan identifies a so called “soft marker”–a minor, usually transient, structural change which may indicate a risk of serious fetal anomaly but which in itself is probably inconsequential.

Ultrasound imaging has improved vastly in quality, and for this reason, and because first trimester scans are now performed more often, the frequency with which “markers” are observed has risen correspondingly. Some markers may well have disappeared by the time of the “routine” scan at 18-20 weeks.

Of those markers indicating pathology, most …