There are currently only two reliable methods of prenatal, prebirth DNA Paternity or genetic testing – Amniocentesis and Chorionic Villus Sampling (CVS). Both are also more typically used to detect birth defects with the fetus. There is generally quite a bit of confusion about both methods of testing. Please allow us to explain:
An AMNIOCENTESIS is a procedure which removes a small sample of amniotic fluid that surrounds a fetus. Amniotic fluid contains fetal cells and waste products which are discharged from the fetus. These cells can provide genetic, or DNA, information just like blood or a cheek swab. The Amniocentesis procedure is performed by an OBGYN by inserting a needle through the mother’s abdomen and into the uterus. Approximately 2 Tbsp of amniotic fluid is drawn out, which is then shipped via overnight mail on blue ice and tested in the laboratory. An Amniocentesis is performed, on average, between weeks 14 and 24 of the pregnancy.
The fluid that is obtained through the draw can be used to test the parentage of the child, or in determining the sex of the child, in addition to screening for over 100 types of disease inherited from the family. Examples of these diseases are Down Syndrome, Cystic Fibrosis, Sickle Cell disease, and Huntington’s disease. While this procedure is routinely performed and can be safe, some risks are involved and the pregnancy can be endangered. This is why most physicians do not want to perform the procedure unless it is medically necessary. (A DNA Paternity test is not deemed medically necessary.)
RISKS: During an Amniocentesis there is the possibility of injury to the mother or the fetus from the needle. The most common injury occurs from puncturing the placenta, but it is also possible that an infection can occur due to the introduction of bacteria into the amniotic fluid, as well as cramping, bleeding and leakage of Amniotic fluid. This procedure also carries some risk of causing a miscarriage and when it is performed prior to 15 weeks. Studies have also shown an increased risk that the fetus will develop clubfoot from the procedure. Unfortunately, all pregnancies have a risk for miscarriage, whether a test was performed or not. In the second trimester (when an amniocentesis is typically performed), the normal risk for miscarriage is between 2-3%. The risk for miscarriage is increased slightly with amniocentesis and the risk of amniocentesis-related miscarriage is 1 in 250 to 1 in 300.
CHORIONIC VILLUS SAMPLING, or CVS for short, is a test that can find certain problems with a fetus. CVS is performed late in the first trimester, most often between the 10th and 14th week.
CVS samples can be collected in one of two ways – either by putting a thin flexible tube (catheter) through the vagina and cervix directly into the placenta (transcervical CVS), or by inserting a long needle through the belly into the placenta (transabdominal CVS), which is similar to the amniocentesis procedure. The method that is used is dependent upon the position of the placenta and uterus. This will be determined the day of the procedure during the ultrasound examination. A thorough ultrasound examination is performed prior to and during the procedure.
The type of sample that is taken during a CVS procedure are the Chorionic Villus Cells. Chorionic Villi are similar to tiny fingers and grow inside the placenta. The genetic material inside these cells are the same as those found in the fetus’s cells.
The reasons for having a CVS performed are the same as those for an Amniocentesis – to determine health of the fetus and parentage, if necessary.
RISKS: Just like the Amnio, there are some risks involved with the CVS procedure. They include infection of the uterus, cramping, spotting, leakage and miscarriage. While miscarriages may occur following CVS, many can be unrelated to the CVS procedure. Studies in the United States and in Europe now suggest that the risk for CVS-related miscarriage is between 1/100 – 1/200.
While both tests offer the possibility of grave risks, the benefits can be educational or rewarding. The knowledge about your baby and it’s health can be good news, if there were concerns, or will have a different outcome which will influence your preparation for a new family member. You might need to make special arrangements for birthing or for the child’s life and care.
When prebirth Paternity DNA Testing is being considered by the mother, her OBGYN must be consulted. The physician will be the one to approve and perform the test and therefore, the mother must begin with a visit to her doctor. As stated above, in most cases, an OBGYN will not want to perform either of these procedures if it is just for a Paternity Test, which is not medically necessary, as the risks can be too great. Some doctors have even told their patients that this kind of test is not even possible. This is not true.
If the mother is already planning on having one of these procedures performed (which should be covered by insurance ) the doctors office will send the samples to a genetics lab for which ever test is needed. That lab can then grow more cells and send them along to a DNA Paternity Testing lab. Mother will usually be granted a prebirth procedure if she has an abnormal ultrasound, has a family history of certain birth defects, has previously had a child or pregnancy with a birth defect, or will be 35 or older at the time of delivery.
If the mother is not planning of having one of the procedures, and her doctor still approves the procedure, she will most likely have to pay the OBGYN thousands of dollars for the procedure, on top of the DNA testing fee and shipping.
In all cases, a prebirth, prenatal DNA Paternity Test begins with a consult at the OBGYN, for methods, risks, approval or denial. DNA Testing is then performed when the mother and possible father have their samples collected, typically via cheek swab, and sent to the Paternity Testing Lab.
