The vast majority of babies are normal. However all women, whatever their age, have a small risk of delivering a baby with a physical or a mental problem. In some cases this may be due to chromosomal problems such as Down Syndrome.
The only way to know for sure whether or not your baby may have a chromosomal problem is by having an invasive test, such as Chorionic Villus Sampling (CVS) or amniocentesis (amnio). However, these tests have a small chance of causing a miscarriage of about 1% (about one chance in 100) for CVS, or about 0.1% (about 1 chance in 1000) for amniocentesis.
This FTS (First Trimester screening) test helps you and your partner decide whether the chances that your baby may have a chromosomal problem is high enough to warrant having an invasive test, such as CVS or amnio.
The FTS test includes:
- Your age
- Nuchal Translucency (amount of fluid behind the neck of the fetus on ultrasound)
- Presence or absence of any physical abnormalities on ultrasound
- Level of two proteins (free beta hCG & PAPP-A) in your blood.
By combining this information, the FTS test can identify about 9 out of 10 pregnancies (90%) in which the baby has Down syndrome. This is more accurate than either the ultrasound part or the blood part of the test done on their own.
Since the blood test for the protein levels is done in our unit, your results will be available immediately. The chances of Down syndrome will then be discussed with you. Only you can decide if you wish to have an invasive diagnostic test based on this risk.
If the thickness of the back of the baby's neck is quite big other problems may be present. These are very rare but include heart problems.This special First Trimester Screening scan also provides other very useful information:
- Accurate dating of the pregnancy
- Fetal heart rate
- Number of fetuses present and, if twins, whether they are identical or not
- Detects obvious fetal abnormalities
It is important to remember that a screening test does not guarantee a normal baby. Therefore you should carefully compare the advantages and disadvantages of a screening test (like FTS) compared with a diagnostic test (like CVS).
Only you can decide if you wish to have an invasive diagnostic test, like CVS, and you will always have the right to choose this definitive test if you prefer. It is also recommended that you have a further scan at 20 weeks to check the baby so that we can reassure you about problems that the CVS cannot detect.