There are several
established methods to screen for Down’s syndrome.
We regard soft marker scanning at 18-22 weeks as
a weak screening method because it has poor sensitivity
for a relatively high false positive rate, and gives
results late in pregnancy. This guideline therefore
aims to recommend a method for dealing with soft
markers discovered during a routine anomaly scan,
rather than recommend soft marker scanning as a method
The absence of soft
markers on ultrasound has little relevance for the
risk of trisomy, and many publications have overstated
the significance of seeing a soft marker. Reporting
these findings can cause considerable anxiety. Furthermore,
it can lead to invasive tests being undertaken unnecessarily,
with the potential of miscarriage associated with
including ultrasound scans, require the consent of
the expectant mother, who should be informed of the
possible findings and consequences of any test. Mothers
need to be aware that the findings of soft markers
may prompt a discussion of chromosomal anomalies.
This booklet details
a list of soft markers, their identification, the
possible implications and further areas to be considered.
The imaging part of this screening process is within
the competence of all professionals currently undertaking
mid pregnancy anomaly scanning. This booklet aims
to ensure that professionals feel able to include
and exclude soft markers, and complete their mid
trimester examination, usually at a single ultrasound
scan. This should reduce the need for internal or
external referral, and increase the reassurance which
can be given to the expectant mother.
The following are considered
to be soft markers. They are dealt with in more detail
in the following sections.
Other findings such
as a 2 vessel cord, the head shape and variations
in the hands and feet are not considered soft markers
in this context.
to report and offer karyotyping
1. Smith-Bindman R, Hosmer BS, Feldstein
MD, Deeks J, Goldberg JD. (2001) Second trimester
ultrasound to detect fetuses with Down Syndrome A
meta analysis. JAMA:285 (8), Abstract