The Quad Screen is an optional prenatal blood test that measures four chemical markers: alpha-fetoprotein (AFP), chorionic gonadotropin (HCG), unconjugated estriol (uE3), and inhibin-A. The test is performed between the 16th and 20th week of pregnancy to determine a patient’s risk for having a baby with NTD, Down syndrome or Trisomy 18. However, the Quad Screen cannot detect the majority of genetic diseases
The human brain and spinal cord are among the first organs to develop, generally within the first month after conception. NTDs form when there is an incomplete closure during development. The normal population risk is 0.1-2960.
Down syndrome (Trisomy 21) is the most common chromosomal abnormality seen. It is characterized by general growth retardation, lack of muscle tone, higher incidence of other abnormalities in a number of organ systems, and moderate to severe mental retardation. Normal population risk is 1 in 800.
Between 16 and 20 weeks gestation.
Generally 7-10 days.
An abnormal result is not definitive. An abnormal result indicates that your doctor will prescribe additional tests such as an amniocentesis or a more detailed ultrasound. If those tests come back abnormal then you and your doctor will be able to prepare for the best way to care for the baby in some cases. Some patients would choose to terminate the pregnancy if the amniocentesis confirmed Down syndrome or a NTD.
A normal test is not a guarantee. The Quad Screen will detect approximately 75% of all ventral wall defects, 85% of all NTDs (neural tube defects) and 80% of all Down syndrome birth defects. Some birth defects can be missed by the test.
Please Note: 95% of all women who undergo prenatal testing receive reassuring news that their babies do not have a disorder. The Quad Screen is just a screening test.
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