Amniocentesis Accuracy

By Ashley | January 21, 2010

An amniocentesis one of the procedures conducted on a pregnant woman to check for the possibility of any birth defects. This test is conducted to check for the chromosomal content of the amniotic fluid of the amniotic sac or to conduct an alphafetoprotein test on the amniotic fluid. The most common reasons for conducting this test is to check for the possibility of Down’s syndrome and other such defects. The test is rather simple in essence but as with any invasive procedure, there is a risk that accompanies the procedure. This risk is that of a miscarriage that occurs as a result of improper healing from the procedure or the risk of infection.

An amniocentesis is conducted to check for chromosomal defects in a growing fetus. Human beings require 46 sets of chromosomes that are inherited from both parents equally. When there is some kind of problem with the structure of these chromosomes or the number of these chromosomes, birth defects can occur. Birth defects that normally can occur during the development of a fetus are usually detected by the human body and the fetus is destroyed. This is the reason for the high risk of miscarriages in the first trimester of pregnancy. The first trimester is considered the fragile period because there is a fine balance of hormones that maintain the integrity of the fetus. Usually, when there is a major defect in the structure of the fetus during this period due to genetic reasons, the mother’s body will destroy the fetus and eject it from the body. This does not happen in the case of some problems like Down’s syndrome.

While the amniocentesis test is considered the standard for checking for chromosomal defects, it is a test that is conducted only after there is a strong suspicion of the possibility of Down’s syndrome. This is something that is initially tested for by analyzing the chromosomes of both parents. Further confirmation is then sought with amniocentesis. The accuracy of the test is quite with estimates varying between 95 and 99%. What this means is that once an amniocentesis is done, the results are nearly always considered a definitive diagnosis. Since the test is performed in the second trimester and rarely, in the first, a couple always has the option of abortion to ensure that a defective fetus is not brought to term. Performing this test in the first trimester also increases the risks of miscarriage due to the procedure.