Aspirin in pregnancy
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Aileen Keigher
Community Midwife Team Leader Whittington Hospital, London
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Miss Claire Mellon - 10 weeks

Combined screening tests

At the same time as your dating scan, you can also choose to have a combined screening test to assess the likelihood of your baby having chromosomal abnormalities. These are conditions in which babies are born with an extra or damaged chromosome in their cells, e.g. Down’s Syndrome. In most cases Down’s syndrome happens by chance, it is not usually inherited.
In Short
Combined screening includes a nuchal translucency scan and a blood test and is offered between 11 and 14 weeks of pregnancy.

The results are compared with the mother’s age as the chance is higher in older mums. These tests don’t give an actual diagnosis. If your chance is thought to be high, you will be offered diagnostic tests to find whether your baby does have Down’s. Some couples don’t want to have these tests and this is entirely their choice.

What happens in a nuchal translucency scan?

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. This test also includes other factors like previous medical and obstetric history if applicable e.g., smoking, IVF pregnancy.

What does the blood test check?

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).

Are there alternatives to combined screening?

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.

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This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Essential Parent has used all reasonable care in compiling the information from leading experts and institutions but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details click here.