Biomedical Engineering Reference
In-Depth Information
Nuchal translucency screening for Down syndrome
In Sweden, as in many other countries, pregnant women are currently
offered a routine ultrasound scan in the second trimester, and this offer is
accepted by a vast majority (97 per cent according to national statistics).
Women aged over 35 are counselled about their risk of carrying a foetus
with Down syndrome on the basis of their age and are offered an invasive
test to examine the foetus, the rationale being that the risk of giving birth
to a baby with Down syndrome increases with maternal age. During the last
decade, medical research has established that there is a strong association
between an increased space of fl uid that can be measured at an ultrasound
examination carried out in gestational weeks 10-14, and Down syndrome.
Drawing on this association, a new non-invasive technique for assessing the
risk for Down syndrome has been developed: nuchal translucency screening
by means of an ultrasound examination (Saltvedt
et al
. 2005).
A fl uid-fi lled space at the back of the foetal neck (nuchal translucency),
which exists only in early pregnancy, is measured in millimetres. Using
software, a risk score is estimated based on this measurement in combination
with maternal age and length of gestation. The main purpose is thus to
identify women at high risk of carrying a baby with Down syndrome, and
to offer these women an invasive test for foetal karyotyping to confi rm or
dismiss a Down syndrome diagnosis. The rational for introducing the nuchal
translucency method is that this method will be more effi cient in predicting
risk for Down syndrome than the current practice based on maternal age. This
can in turn reduce the total number of invasive tests that have to be carried
out to confi rm chromosomal abnormality, tests that are not unproblematic
as they also cause a certain number of miscarriages.
As this ultrasound screening is still fairly new, women's experiences
have not yet been studied to any great extent. A survey that was part of a
randomized controlled trial in Sweden indicated that just taking part in the
ultrasound screening did not cause more disturbed emotional well-being or
worry about the baby's health than a routine scan (Georgsson Öhman
et al
.
2004). However, some in-depth qualitative studies of psychological reactions
in women who received false positive results (indicating chromosomal
abnormality) showed that these women expressed strong feelings of anxiety,
which for some also lasted after confi rmation of normality and after the
birth of a healthy baby (Baillie
et al.
2000; Georgsson Öhman
et al.
2006).
The case of false positive screening results is an inevitable part of all
screening procedures, an outcome that will question normality in a more direct
way and take on particular importance (Davison
et al
. 1994). In this chapter,
we will explore pregnant women's understanding of false positive screening
results, more specifi cally women's ways of understanding information about
being at high risk of carrying a foetus with Down syndrome after ultrasound
screening. We will draw on interviews with 20 women
6
who received a high
risk result at the ultrasound scan, in this study defi ned as a risk of 1:250 or
