Types of Prenatal
Testing
Prenatal
screening tests can tell you the chances your fetus may have certain genetic
disorders or birth abnormalities, such as sickle cell disease, Down syndrome,
spina bifida, cystic fibrosis, Tay-Sachs disease and others. Prenatal
diagnostic tests can tell you if it actually does.
There
are a variety of prenatal screening tests:
·
Carrier screening: This is a blood test parents can undergo
prior to or during pregnancy to determine if they are carriers of genes that
cause conditions like cystic fibrosis or sickle cell. If both parents are
carriers, there is a higher risk of the fetus having a severe form of the
disease.
·
Chromosomal screening: The mother’s blood is tested to
analyze the small amounts of fetal DNA present and the various protein levels
to determine if there are missing or extra chromosomes in the fetus. This can
tell you about the likelihood of conditions such as Down syndrome or Turner’s
syndrome.
·
Screening for physical abnormalities: Ultrasound and blood
tests can be used to help determine the risk of conditions like abnormal fetal
heart formation, birth defects, neural tube defects (like spina bifida and
anencephaly), and issues with the development of the brain, skeleton, kidneys,
abdomen, face and limbs.
Based
on the risk level suggested by screening tests, your provider may recommend
prenatal diagnostic testing to provide more definitive information. Diagnostic
testing is also a consideration if you have a personal or family history of
genetic conditions, are over age 35 or have a history of miscarriages or
stillbirths.
The two most common forms of diagnostic tests are amniocentesis, in which a needle is used to extract amniotic fluid from the amniotic sac surrounding the fetus, and chorionic villus sampling (CVS), in which a needle is used to remove cell samples from the placenta, either through your abdomen or vagina.
Key Considerations
Some
level of anxiety is typical during pregnancy, so it can be helpful to consider
what you will do with the test results once you have them. You may decide to
proceed with screening tests for the reassurance a result within the standard
range can provide, but you should be prepared if that is not the case.
Based
on your medical history and personal beliefs, it’s up to you whether or not to
have prenatal testing and which types. Some things to keep in mind:
·
Prenatal
screening tests only measure risk, and there is always a chance the results are
wrong. In addition, diagnostic testing can’t always determine the severity of
some conditions. Talk to your provider about the accuracy rates for tests you
are considering.
·
There
is no medical risk with prenatal screening tests; however, diagnostic tests
carry a slight risk of infection, bleeding and miscarriage.
·
Different
tests can only be performed at certain stages of pregnancy, so there may be a
delay between the results of a screening test and the time when you can have a
diagnostic test, if you choose. The results from some tests are available in
days, while others take several weeks.
·
Diagnostic
testing can provide information that will impact your care and choices during
pregnancy. It can also help you and your care team prepare for your baby’s
treatment and care after birth.
Your
women’s health provider can offer information and resources to help guide your
decisions, including a referral to a genetic counselor specially trained in
the nuances of genetic testing and results.
Our
providers pride themselves on giving compassionate, knowledgeable and
non-judgmental care. If you have questions or concerns about your pregnancy,
bring them with you to your next prenatal visit or call us to schedule an appointment.
