Can You Get a DNA Test While Pregnant?
It is possible to take a sample of a developing baby's DNA while still pregnant. This procedure is called amniocentesis. According to the Mayo Clinic, doctors perform about 200,000 of these procedures every year, but there still are sufficient risks. The most common reason for a DNA test before birth is to screen for birth defects, but the test also can show the presence of infection, lung maturity or even can determine paternity.
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Function
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Amniocentesis uses amniotic fluid, which contains cells shed from the baby, to obtain DNA. It detects chromosome abnormalities such as Down syndrome or trisomy 21, neural tube defects such as spina bifida and genetic disorders such as cystic fibrosis.
The procedure is performed with continuous ultrasound while the mother is on her back. A hollow needle is inserted into the uterus and withdraws a small amount of amniotic fluid. The mother may experience some cramping, but amniocentesis generally is painless.
Time Frame
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The test typically is used to test for genetic disorders in the second trimester, between 15 and 20 weeks. An earlier amniocentesis can have a higher risk of miscarriage. It also can be performed in the third trimester to test for uterine infection if the membranes have ruptured prematurely or to assess lung maturity before electing to deliver a baby for another health problem. It also can detect the severity of anemia in babies with Rh disease.
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Considerations
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Amniocentesis results are 98 percent to 99 percent accurate for the diseases it tests for, but a DNA test is not a guarantee of a healthy baby.
In some cases, testing may not be the best option. For instance, some parents would not change the course of the pregnancy, no matter what the results, because of religious or moral reasons. For others, the small risks associated with the procedure are not worth the information that is gathered.
In the case of paternity testing, it often is recommended that the test is delayed until the baby is born, but there may be pressing circumstances, such as a court order, that would make amniocentesis necessary.
Benefits
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Despite the risks, some families may choose to have a DNA test performed, especially if the results would impact the course of the pregnancy. Some genetic defects might cause the parents to question carrying the baby to term or would present the need to prepare mentally or physically before the birth. Sometimes interventions can be made before the baby is born, such as surgery for spina bifida or blood transfusion for Rh disease, that require a diagnosis.
Warning
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Amniocentesis brings a risk of miscarriage or uterine infection. The risk of miscarriage is relatively small, less than 1 in 500 to 1 in 300 according to the American College of Obstetricians and Gynecologists. Because of this risk, amniocentesis is only performed when deemed necessary and is not used routinely.
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