Down Syndrome Site : Types of Down Syndrome Screening

Having a baby is an exciting time, whether it's your first or your fifth. It is only natural to feel optimistic and assume everything will be fine. However, if you are over 35, if you smoked while taking oral contraceptives or if Down syndrome runs in your family, then you may want to opt for Down syndrome screening so you know what to expect. Down syndrome is the most common genetic birth defect, affecting 1 in 800 babies.

When a doctor performs the initial Down syndrome screening, he'll check an ultrasound for enlarged tissue behind the baby's neck, which may indicate something is amiss. Next, he'll examine a blood sample for several components indicative of a Down syndrome baby. Normally, a certain amount of alpha-fetoprotein made in the womb makes its way to the blood stream, but in Down's babies, the amount is decreased because the fetus is smaller than usual. The hormone estriol is also decreased in a Down syndrome pregnancy. A part of the human chorionic gonadotropin hormone (specifically the beta subunit) and the level of inhibin-A protein are increased. Trace levels of PAPP-A protein may also emerge if the baby has Down syndrome. Of course, none of these tests are 100% accurate.

The second type of Down syndrome diagnostic tests are about 99% accurate in detecting signs of this chromosomal disorder. However, these procedures are more invasive and sometimes result in a miscarriage or other complications. Typically, doctors only perform these tests on women over 35, if genealogy warrants it or if they've tested positive in the initial screening. Amniocentesis, performed from 16 to 20 weeks, uses a needle to remove a small amount of amniotic fluid from the womb.

While it's an out-patient treatment, women may experience cramping, bleeding and infection, not to mention that 2-3% of patients lose their baby. As a result, amniocentesis is not recommended before the 14th week of gestation. Chorionic villus sampling and percutaneous umbilical blood sampling are other alternatives.

Once the baby is born, the doctor can do a physical Down syndrome screening. To verify the diagnosis, doctors sometimes check the karyotype. By looking at a stained blood tissue sample, the doctor can analyze chromosomes grouped by size, shape and number to confirm the Down syndrome diagnosis. If your baby is one of the many born with this genetic condition, then you can take comfort knowing there are many resources to assist you, such as the National Down Syndrome Society or the National Association for Down Syndrome.

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