Amniocentesis and Chorionic Villus Sampling
Amniocentesis
In some cases, abnormalities in the development of a fetus can be diagnosed by ultrasound alone. In many cases, however, diagnosis will require a physician to perform an invasive procedure during pregnancy. Chorionic Villus Sampling (CVS) and amniocentesis are the two main types of invasive tests performed during pregnancy.
Both types of procedure are performed under ultrasound guidance. CVS is a procedure in which a small portion of the placenta is removed, either by placing a thin catheter through the cervix into the uterus, or by placing a small needle through the belly. CVS is generally performed from 10-13 weeks.
Chorionic Villus Sampling
Amniocentesis is a procedure generally performed in the second-trimester, starting at 15 weeks. A thin needle is placed through the belly into the amniotic fluid sac, and a small amount of amniotic fluid is removed.
In rare cases, fetal blood must be obtained to identify certain conditions. Fetal blood sampling is performed starting in the second trimester.
Most women undergoing CVS or amniocentesis do so to detect chromosomal abnormalities, such as Down syndrome. Some women choose one of these tests following blood tests or ultrasound findings that indicate a high-risk of a particular chromosomal abnormality. Other women choose to undergo testing even if the risk for chromosomal abnormalities is very low, since only invasive testing can definitively identify these conditions.
Other women undergo CVS or amniocentesis to detect certain genetic conditions, such as cystic fibrosis, Tay-Sachs, or Sickle Cell Disease. This may be suggested if blood tests indicate that the parents are carriers for certain conditions.
Physicians at the Perinatal Center are skilled at performing CVS, amniocentesis, and fetal blood sampling. We work closely with the Division of Human Genetics to identify couples at risk of having a child with genetic conditions, and to ensure that the most thorough information is obtained.