Amnio & CVS… What are they?
Amniocentesis
An amniocentesis is available for women over 35, for women with a family history of genetic disorders, and for expectant mothers who have had a quad-screen suggesting the possibility of a genetic disorder.
Amniocentesis diagnoses the possibility of:
- Chromosome problems (such as Downs syndrome)
- Genetic diseases (such as cystic fibrosis, sickle cell disease)
- Neural tube defects (such as spina bifida)
Aside from testing for chromosomal abnormalities or birth defects, an amniocentesis can also test the baby’s lungs to see if they are mature if the mother is showing signs of premature labor, or if the mother will need to be induced early. The amniocentesis can also determine the sex of the baby.
How is it done?A needle, guided by ultrasound, is inserted through the abdomen into the amniotic sac to collect fluid surrounding the baby. The amniotic fluid holds cells shed from the baby, and is an accurate way to test for chromosomal abnormalities and some birth defects.
Results can be had in about 2-4 weeks, and findings are quite accurate.
Amniocentesis is not without risk. It can cause miscarriage in about 1-2 pregnant women out of 200. There is also an increased risk of infection.
Chorionic Villus Sampling (CVS)
Having a CVS done will diagnose chromosomal abnormalities, such as Downs syndrome, Tay-Sachs disease, cystic fibrosis, or sickle cell anemia. Because the placental tissue does not include amniotic fluid, some birth defects, such as spina bifida, can not be tested for.
How is it done?A thin tube, guided by ultrasound, is inserted through the cervix and up to the placenta where a small amount of the placental tissue is removed (B) OR tissue is removed via a needle inserted through the abdomen (A) similar to the amniocentesis.
This is generally done between 10-12 weeks, and is available for women who will be 34 years of age or older when they deliver, or for those with a family history of genetic disorders diagnosed by CVS. The CVS is not routinely available for pregnant women, and a meeting with a genetics councilor is required prior to the procedure. CVS is considered more risky than the amniocentesis, causing more miscarriages, limb defects, and also carries the risk of infection. Results can also be confusing to read, requiring more testing to understand the results. CVS is not as accurate as the amniocentesis, but the benefit for some is the chance to learn early in pregnancy that there could be chromosomal abnormalities.