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Maternal Serum Screening

Down Syndrome, Trisomy 18 and Neural Tube Defects

What is Maternal Serum Screening?

Slide 2

March 2011

The goal of current maternal serum screening programs is to identify women at increased risk of having a baby affected with Down syndrome, trisomy 18 or neural tube defects and that will benefit from diagnostic testing. By performing diagnostic testing only in this high risk population, the likelihood of identifying an affected fetus will be higher than if a diagnostic procedure is performed in the unscreened population. The ultimate goal is to have fewer invasive procedures as well as fewer procedure related losses of normal fetuses. When a woman at high-risk or with a positive screen is identified, genetic counseling and a diagnostic procedure such a chorionic villus sampling, or CVS, or amniocentesis is offered to determine if the fetus has the genetic defect.

Maternal screening is not without disadvantages. The results provide a risk but not a diagnosis. Chorionic villus sampling or amniocentesis needs to be performed to determine whether the fetus is affect by Down syndrome, trisomy 18. Ultrasound and measurement of amniotic fluid alpha-fetoprotein (AFP) is used in the diagnosis of neural tube defects.

Although the current screening approaches have relatively high detection rate, depending on the test performed, about 5% to 20% of affected babies will not be identified. In addition, not all chromosomal conditions will be detected which is in contrast to CVS or amminocentesis where all autosomal trisomies are detected.

What is Maternal Serum Screening?


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