Screening For Chromosomal Abnormalities
Screening tests can be performed in order to collect a variety of information, including the risk of a chromosomal abnormality. Most of these tests are relatively non-invasive and do not carry a high amount of risk. Sometimes though, these tests are not conclusive. Depending upon your age and medical history, your health care provider may recommend one or more of the following tests.
Serum Screening Test
The maternal serum screening test is a blood test that can help determine if there is a high risk for Downs Syndrome, Edward's Syndrome or neural tube defects in a pregnancy. Blood is taken from the mother's arm and the serum (the watery part of the blood) is tested. This test does not confirm a chromosomal abnormality, but only indicates whether there is an increased risk of your baby having one. This test is usually performed sometime between the 15th and 18th week of pregnancy.
If your risk factor is low, you probably won't need to have any more tests. If you find that you have an increased risk factor, you may opt for a diagnostic test. Diagnostic tests do carry some risk of miscarriage, so it is important for mom to carefully weigh her decision.
Nuchal Translucency Measurement
This test uses an ultrasound to measure the amount of fluid at the back of a baby's neck. Babies with Downs Syndrome tend to have more fluid. This information combined with the mother's age can give a good idea of the risk factor for a chromosomal abnormality. This test is usually performed between 11 and 14 weeks.
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