Amniocentesis & Chorionic Villus Sampling

Prenatal Genetic Screening

There are many tests available to provide information about whether a fetus has certain genetic disorders or other abnormalities before birth. Screening tests serve to give information about the chance of being affected, while diagnostic tests serve to tell us if this is actually the case or not. Both screening and diagnostic tests are available to all pregnant women.

Genetic disorders are caused by our chromosomes. Chromosomes contain our DNA and are present in every cell. They are what make each of us unique. Many genetic disorders are inherited, meaning they are passed on from one’s parents. At the first prenatal visit, the clinician will take a family history to make further recommendations about prenatal genetic screening. This is usually done through a blood test of the pregnant patient and sometimes the father of the baby. The blood that is collected contains cells from the pregnancy that have crossed into the mother’s blood. An ultrasound of the baby is also helpful to look for certain anatomical abnormalities associated with different genetic disorders. A negative test means the baby is unlikely to be affected, while a positive test means further diagnostic testing may be needed. Diagnostic tests are more definitive. Such tests are usually only offered when screening tests and ultrasound results are strongly suggestive of a genetic disorder or other birth defect. An example of a diagnostic test is an amniocentesis, which involves using a needle to remove a small amount of fluid surrounding the baby. This fluid is then examined to look at the baby’s chromosomes. Given the improved screening tests available today, diagnostic testing like amniocentesis is not used as frequently as it once was.

It is important to note that all testing is completely optional. Fortunately, most babies are born healthy, and all babies are born wonderful! Some parents want to know beforehand if their baby is affected by a disorder or certain health concerns, while others do not. As health care professionals, we are here to guide you in this process.