As part of your antenatal care
we are offering to do a scan of your pregnancy.
The first scan will be done at your antenatal
visit. It is to check how many weeks pregnant
you are, that there are not twins and that the
baby is doing well. Usually the scan will be
through your abdomen and you should have a full
bladder. Sometimes the scan will be done through
the front passage (vagina) but the ultrasonographer
will talk to you about this if it proves necessary.
A second scan, done at about 20 weeks, is to
check that your baby is normal. Most babies are
healthy, but sadly some have problems which could
be serious. If you really do not wish to know
if the baby has an abnormality, it may be best
to decide not to have this scan. If you do decide
to have a scan we will assume that you wish to
know about anything that we find.
The scan will involve you lying down on a couch,
and a trained scan operator putting first scan
gel and then the scan head onto your abdomen.
This will give images on the screen which allow
measurements of the baby and give moving pictures.
These can be quite difficult to see clearly,
but the scan operator will try to ensure that
all is well.
About half of the major abnormalities which
cause serious difficulties will be seen on a
scan and half will not be seen. This means
that even if your scan is normal there is a small
chance that your baby will still have a problem.
Below is a list of different types of congenital
abnormality, and how likely scanning is to identify
each problem.
| Problem |
What the problem is |
Chance of being seen |
| Spina bifida |
Open spinal cord |
90% |
| Anencephaly |
Absence of the top of the head |
99% |
| Hydrocephalus |
*Excess fluid within the brain |
60% |
| Major congenital heart problems |
|
25% |
| Diaphragmatic hernia |
A defect in the muscle which separates
the chest and abdomen |
60% |
| Exomphalos/gastroschisis |
Defects of the abdominal wall |
90% |
| Major kidney problems |
Missing or abnormal kidneys |
85% |
| Major limb abnormalities |
Missing bones or very short limbs |
90% |
| Cerebral palsy |
Spasticity |
Never seen |
| Autism |
|
Never seen |
| Down syndrome |
May be associated with heart and bowel
problems |
About 40% |
| * Many cases present late in
pregnancy or even after birth |
The scan can sometimes tell what sex the baby
appears to be, but not always, and we would usually
not do extra scans just to identify the sex of
the baby. If the scan does predict the sex of
the baby, this is correct about 95% of the time.
The scan operator will only tell you the sex
of the baby if you, and all the people in the
scan room with you, want to know that information.
If the scan finds a problem you will be told
at the time of the scan that there is a problem,
but a full discussion of the problem may require
you to come back to the hospital for a further
scan and discussion with a specialist. Most problems
that need repeat scanning are not serious and
approximately 15% of scans will need to be repeated
for one reason or another.
