Testing for Possible Birth Defects

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A woman’s blood can be screened for the possibility that her child could have certain birth defects. A birth defect is a physical or mental abnormality that occurs in the womb or at conception. In most cases, the cause of a birth defect is unknown, however, some are a result of genetics or chromosomal abnormalities. It is important to remember that the results of screening tests cannot be used to make a diagnosis but can indicate when further testing should be done.

Screening tests are voluntary but are often recommended for mother’s of a certain age or for people who have a family history of birth defects or chromosomal disorders. During the first trimester, a simple blood screen and ultrasound can be done to detect the risk of Down syndrome and trisomy 18, which are both chromosomal disorders. During the second trimester, another simple blood test may be performed to measure the levels of certain substances excreted by the baby’s liver or the placenta. If the test measures three specific substances, it is called a triple screen, and if it measures four specific substances, it is called a quad screen. Results of these screens may indicate the risk of carrying a baby with conditions such as spina bifida, Down syndrome, or anencephaly.

Diagnostic Testing is recommended only if a risk is detected by a screening test. One diagnostic tool is a level II ultrasound, which allows a doctor to thoroughly examine every inch of a developing baby’s body.