The Nuchal Translucency Scan - This is arranged for between 11 and 14 weeks of pregnancy. The thickness of a layer of fluid under the skin at the back of baby's neck is measured. Babies with Down Syndrome tend to have a slightly thicker fluid layer than other babies possibly because of how lymph fluid is drained under their skin.
This measurement is combined with your age related risk to produce a personal risk for you. This is an ultrasound based test and is completely safe. No x-rays are used.
The scan can also recheck your due date, confirm a heart beat is present and occasionally pick up other abnormalities in baby.
Serum Test - This is a blood test done at 14 to 18 weeks of pregnancy. The concentrations of three hormones are measured. These levels tend to be slightly different in women carrying a baby with Down Syndrome. These results and your age are combined to give you a personal risk for carrying a baby with Down Syndrome.
Integrated Screening - The results of a nuchal translucency scan and serum test can be combined to produce a more accurate assessment of your personal risk of having a baby with Down Syndrome. The integrated test will pick up more babies with Down Syndrome and allow more women to avoid an amniocentesis than just the nuchal scan or serum test on their own.
Older women sometimes prefer to proceed straight to amniocentesis but it is important to realise that even women in their early forties will frequently find that their screening test results are sufficiently reassuring that they decide not to have an amniocentesis.
