The OSCAR (One Stop Clinic for the Assessment of Risk) is a test comprising of a nuchal translucency scan and a blood test taken at the same time. This is done between 11-14 weeks. It measures levels of hCG (a pregnancy hormone called human chorionic gonadatrophin) and PAPP-A (Pregnancy Associated Plasma Protein) in your blood.
Pregnancies affected by Down's syndrome tend to have higher hormones and lower proteins than normal. NT scans alone can pick up 75 per cent of Down's babies, but by combining with the blood test, the detection rate is 90 per cent (Spencer et al 2003). If the predicted risk is greater than 1 in 300, it is termed as positive indicating an increased risk for Down syndrome and warrants further testing by invasive methods like CVS / Amniocentesis. This will finally determine whether the baby is affected or not. If the predicted risk is less than 1 in 300, it is termed as negative. This means the chances of having Down syndrome is low, but does not definitely exclude it. In case of screen negative result , no further testing is offered.Tests are available at various hospitals around the country and your Midwife and your local surgery will be able to advise you, but you can phone the Fetal Medicine Centre in London on 020 7486 0476 for a list of accredited centres.
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