Prenatal diagnosis refers to a group of procedures that may be considered during your pregnancy to obtain a sample of fluid, placenta tissue or fetal blood directly from the pregnancy for the purpose of performing specialized laboratory tests to accurately diagnose, or evaluate the fetus for conditions demonstrated to be at an elevated risk or likelihood. Prenatal diagnostic procedures allow the maternal fetal medicine team to confirm or exclude these risk factors and utilize the information to tailor further management of the pregnancy. While these procedures are highly accurate, the procedures themselves carry a small risk of complication. Therefore, careful discussion of the risks, benefits and limitations of these procedures is an important part of the decision making process.
Chorionic Villus Sampling (CVS)
This diagnostic test helps identify chromosome abnormalities, such as Down syndrome, and inherited disorders in pregnancies known to be at increased risk. During a CVS procedure, some of the chorionic villi cells are removed from the placenta. There are two ways to collect these cell samples:
- Transcervical – ultrasound-guided thin catheter through the cervix
- Transabdominal – ultrasound-guided thin needle through the abdomen
Amniocentesis can help detect or identify the cause of certain birth defects, specifically those related to chromosome changes or certain DNA abnormalities. The cells that are required to perform this test are found in the amniotic fluid that surrounds fetal development. Amniocentesis may additionally be performed to evaluate whether fetal lungs are mature to assist in delivery planning. The fluid- and the cells within it- is collected by passing a needle through the mother’s abdominal wall into the amniotic sac while monitoring on ultrasound. The fluid sample is then sent to a laboratory to perform specific genetic studies depending on the reason for testing.
Percutaneous Umbilical Blood Sampling (PUBS)
Percutaneous Umbilical Cord Blood Sampling (PUBS), also known as cordocentesis, examines the fetus’ blood, most commonly to diagnosed blood related disorders. During cordocentesis, an ultrasound-guided thin needle is inserted through the abdomen and uterine walls to the umbilical cord, where a small sample of fetal blood is drawn. The blood sample is then sent to a lab for analysis. This procedure is very similar to amniocentesis, except a provider retrieves a blood sample instead of an amniotic fluid sample.
PUBS may also be used to diagnose and treat a fetus who is anemic (low iron levels) for a variety of reasons. Using this technique, the fetus receives a blood transfusion.
For more information about our prenatal screening and diagnostic services, or to schedule an appointment, contact us.