Three prenatal tests can determine if Fragile X is present in the fetus. Chorionic villi sampling (CVS) involves extracting a tiny amount of fetal tissue at 9 to 11 weeks of pregnancy. CVS is not widely used and carries a 1-2 percent risk of miscarriage following the procedure.
Amniocentesis is the removal and analysis of a small sample of fetal cells from the amniotic fluid. Amniocentesis is widely available and involves a lower risk of miscarriage. However, amniocentesis cannot be done until the 15th to 18th week of pregnancy and it usually takes an additional 2 to 4 weeks for the cells to grow and be analyzed. So a woman may have to wait until the 17th to 22nd week of her pregnancy to have the results of this test.
The third method, percutaneous umbilical blood sampling (PUBS), is the most accurate method and can be used to confirm the results of CVS or amniocentesis. However, PUBS is not widely available, PUBS is not done until the 18th to 22nd week and carries the greatest risk of miscarriage.
I was doing some further reading on CVS and I read that The CVS procedure collects larger samples and provides faster results than amniocentesis. The results may be received between one to seven days. A lot of time, CVS may be chosen over amniocentesis because it may be performed earlier in the pregnancy and the mother does not have to risk sticking a needle into her stomach. Instead a Transcervical method can be taken in which an ultrasound guides a thin catheter through the cervix to the placenta. The chorionic villi cells are gently suctioned into the catheter.
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