Medical Tests: Prenatal tests

Prenatal tests: Testing of a fetus for disease before it is born
Introduction: Antenatal testing (or "prenatal testing") involves testing a fetus for a particular disease or condition before it is born. Most antenatal testing is for genetic diseases including chromosomal diseases. For example, older mothers at risk for the chromosomal disease Down syndrome can have various antenatal tests. In many cases, antenatal testing involves physically extracting a small amount of amniotic fluid or fetal tissue, although some diseases have alternative non-invasive antenatal tests. For example, Down syndrome testing can be done via amniocentesis or chorionic villus sampling (CVS), but there are also other non-invasive antenatal ultrasound tests that can be used. Many parents who are afflicted or carriers of genetic disease may use antenatal genetic testing to determine if the fetus is afflicted. Since DNA exists immediately from conception, a genetic test of the fetus at any time should show the correct results.

In many cases, the only possible resolution for a positive test result (i.e. if the fetus is affected) is to terminate the pregnancy. Since all of these procedures carry some risk of premature termination of an unaffected fetus, it is an unnecessary risk if elective termination of pregnancy after a positive result is not acceptable to the parents. Antenatal testing purely for peace of mind creates a risk to the fetus. Also note that a positive test result may need to be repeated, to avoid wrongly terminating the pregnancy in the (unlikely) event of an erroneous false positive in the testing.

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