Some obstetric ultrasound findings are considered variants of normal but are noteworthy because they also increase the risk for underlying fetal aneuploidy. These findings are known as “soft markers” and should be considered distinct from fetal anatomic malformations and (or) growth restriction that also increase perinatal and genetic risks. A soft marker is something which may be seen at the time of the 18-22 week scan which may indicate an increased chance that baby has Down’s syndrome or another chromosome anomaly but which in itself is probably of little or no significance
How high is that risk?
The risk is dependent on a number of factors these includes which soft marker has been seen, if it is seen on its own and what is your prior risk of having a baby with downs syndrome based on your age and history.
Soft markers are common and will frequently be seen on a 20 week scan. In fact about 1 baby in 30 will have a soft marker. The vast majority will not cause any problem at all. However, what has been observed in the past is that particular marker has been seen more frequently in babies with say Down syndrome than in the “normal” population. This has allowed to calculate the risk of individual’s baby having Down syndrome. If after this calculation they opt to have an invasive test and this is reported as normal then the finding becomes irrelevant. Because soft markers are frequently seen in normal babies.