Between ten and 20 weeks, a pregnant woman is offered a series of tests to see how she and her baby are doing.
As well as the earliest ultrasound scan of the baby (usually done at around 11 weeks but sometimes earlier or later), which is aimed at giving a more accurate expected due date for the birth and to formally confirm the pregnancy, a woman usually has a series of blood tests. All tests are optional, but they ensure that the mother has no health issues which might affect her or her baby as the pregnancy progresses.
Most blood tests establish whether or not the woman has any sexually transmitted diseases, or any pre-existing blood conditions which might affect the pregnancy. However, a woman will also be offered the 'double' or 'triple' test. This test looks for a make-up in her blood, which can offer a heightened or lessened risk of her child having Down's syndrome.
What happens if a triple test proves a high risk?
A woman's age at the expected due date is taken into account when looking at the heightened risk of having a child with Down's syndrome. And although it is possible to have a child with Down's syndrome when you are young, the chances increase after the mother is 35. (For example, the chance of having a Down's child at 20 is 1 in 1700, at 30 it is 1 in 900, at 35 it is 1 in 400, and by 45 it is 1 in 35.)
If the mother is told the risk is relatively high, she will be offered a further investigative test, called an amniocentisis which is a more invasive test, because it involves taking a sample of the amniotic fluid from the womb, with a needle.
This test in itself carries a risk of miscarriage.
The nuchal scan
There is now a much safer way of testing for Down's syndrome, called a nuchal fold scan. This is done by ultrasound which is completely non-invasive.
The scan looks at the thickness of the baby's neck to see how much fluid is there. This can tell doctors if there is an increased likelihood of the child being Down's. (A further test is sometimes offered to look for the nose bone, a factor which can suggest Down's syndrome is likely.)
The nuchal scan is not routinely offered free of charge on the NHS and its availability can vary from area to area. In some areas, your health authority or trust may offer it if there is a family reason why Down's syndrome may be more likely, or if the mother is over 35 already.
This test has to be done between ten and 13 weeks, so do not wait for your first midwife 'booking in' appointment to discuss it (as these appointments can take place when ti is already too late to arrange the scan), instead ask your GP or midwife team about it by phone, earlier.
All these tests can only offer a 'risk of' chance, rather than confirm that the child will definitely have a specific condition.
What if the chances of Down's syndrome are likely?
Although people with Down's syndrome do tend to have ongoing health issues, these are not always severe and are increasingly easily managed. Children and adults with Down's are in many ways happy and healthy and it is not necessarily a condition which every parent needs to fear.
Couples who find that their child has an increased likelihood of Down's syndrome can be offered the opportunity to have the pregnancy terminated.
Many argue that if you have already decided that you would NOT terminate a pregnancy if you were handed such news, then there is no point even doing the blood test, because you are only going to cause yourself worry about a possibility of a condition being present at birth.
Others argue that you can prepare for the condition if you are more aware of the chances of your baby having it.
It is a completely individual choice, but one you should discuss fully with your partner and consultant, before taking the first steps towards testing.
