Genetic screening is available for anyone who requests it. You may have had a family history of some defects you are concerned about or may be concerned due to advanced maternal and/or paternal age. Genetic screening involves either blood or ultrasound testing looking for specific types of defects. Please keep in mind that testing may result in both false positive and false negative test results. No test serves as a guarantee and up to 10% of babies with chromosomal problems will not be detected with screening.
HOW AND WHEN GENETIC SCREENING IS DONE
NUCHAL TRANSLUCENCY – This is the most accurate way of screening for chromosomal abnormalities and is a combination of sonography and a blood test done on the mother. The test is done at approximately 12 weeks of gestation. This allows a greater detection rate in the first trimester than the second trimester triple screen and allows the option of first trimester prenatal diagnosis. The test takes into consideration the age of the mother, the fetal heart rate, the nuchal translucency (the amount of fluid behind the neck of the baby), and the levels of B-HCG and PAPP-A (blood proteins found in the mother’s blood). This test can identify >90% of Down syndrome, Trisomy 18, and Trisomy 13. It will not pick up neural tube defects which are most accurately detected with sonography at approximately eighteen to twenty weeks gestation.
Genetic testing is available but you are not required to have it done. It is a personal decision. If these tests show you are at increased risk of having a child with a chromosome abnormality, it does not necessarily mean a problem has been diagnosed, but that further evaluation is indicated. These tests may cause much anxiety along with additional expense. Factors in making the decision to test or not or how aggressively to test must include the risk factors for the baby that are involved in the test.
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