Detailed Anomaly Scan
Most
women are offered a detailed ultrasound scan at 18-24 weeks to see if your baby
is developing normally.
Why have a Detailed anomaly scan?
The vast
majority of babies are normal. However all women, whatever their age, have a
small chance of delivering a baby with a physical or a mental problem. Many
such abnormalities can be diagnosed and ruled out with the Detailed Anomaly
Scan. Reasons to have this scan include:
- To reassure you that your baby is likely to be normal
- To confirm the gestational age of your pregnancy
- To confirm the number of fetuses and, if twins, whether they are identical or not
- To detect birth defects, such as a spina bifida or heart problems
- If you are concerned about the chances of chromosome problems like Down syndrome, this scan can search for subtle markers that may suggest a higher risk that your baby may have one of these problems
- If you want to know your baby's gender this can usually be seen at this scan
When you
attend for this scan we will tell you about everything that we see, unless you
advise us that there are certain things that you don't want to know about, such
as your baby's gender or markers for chromosome problems.
What can this scan detect?
This
ultrasound scan is very accurate but unfortunately it cannot diagnose 100% of
congenital abnormalities. If the scan is complete, we would expect to pick up
at least 95% of cases of spina bifida, 80% of cases of cleft lip or palate, and
60% to 70% of cases of congenital heart disease.
This scan
can also identify 50% to 70% of cases of Down syndrome, but the First Trimester
Screening (FTS) test is better for this. Because 30% to 50% of cases of Down
syndrome appear normal on ultrasound, only an amniocentesis can give you this
information for certain. It is also important to realise that ultrasound scans
in pregnancy do not detect problems like cerebral palsy or autism.
Sometimes
babies with chromosomal abnormalities have signs called ultrasound markers.
These include thick skin in the neck, excess fluid in the kidneys, short arms
or legs, white spots in the baby's heart or abdomen, or choroid plexus cysts in
the brain. While some babies with chromosomal abnormalities have these markers,
it is important to remember that many normal babies also have these signs.
The only
way to diagnose or exclude a chromosomal problem for certain is to have an
amniocentesis. If you would prefer not to know about these markers please
inform us prior to the scan. If the scan suggests a problem, you will be told
this immediately. You will be able to discuss the findings immediately with a
consultant who specializes in fetal medicine.
A full
support service will be available for you should any problems be detected,
including a referral to an appropriate pediatrician. A copy of your report will
be sent to your referring hospital, doctor or midwife to ensure good
communication.
