The results are compared with the mother’s age as the risk is higher in older mums. These tests don’t give an actual diagnosis. If your risk is thought to be high you will be offered diagnostic tests to find whether your baby actually does have Down’s. Some couples don’t want to have these tests and this is entirely their choice.
This is a screening scan that measures the thickness of the fluid in the nuchal fold at the back of the foetus’s neck. It is thicker in a foetus with Down’s, possibly due to less efficient circulation system. The test combines the thickness of the fold with your age to assess the statistical chances that the baby has Down’s syndrome.
The blood test checks for levels of free beta-hCG (human chorionic gonadotropin) and placenta associated plasma protein A (PAPP-A) hormones that might indicate the possibility of Down’s syndrome.
Together these results help to calculate the statistical likelihood of your baby having Down’s Syndrome (the most common chromosomal disorder).
If you miss your chance to have the combined screening test you can have the quadruple test – a blood test that screens for levels of pregnancy hormones hCG (human chorionic gonadotrophin), uE3 (oestriol), AFP (alpha fetoprotein) and inhibin A in the blood as the levels tend to be higher in mothers carrying a baby with Down’s Syndrome. Alternatively, there is a private test that can be done from ten weeks into your pregnancy called non-invasive prenatal screening, or NIPT. Clinics offering the tests claim they are highly accurate at detecting risk for Down’s syndrome. The test also looks for Edward’s syndrome, Patau syndrome and Turner syndrome. The NHS states that “further research and evaluation is necessary before these tests are introduced into the NHS, although they are already available in the private sector”.