When you're expecting a baby, you can also expect to have lots of medical tests. Ultrasound imaging, glucose monitoring and other health checks are a routine part of every pregnancy.
There are reasons you might want to consider
genetic testing too. For example, you may wonder whether a health issue that runs in your family will affect your child. If you're 35 or older, you might worry about risks for genetic issues (which rise with age).
Whatever your concerns, keep in mind that genetic testing is 100% optional. Your decision may reflect your personal beliefs, your family health history and the advice of your health care team.
How genes can influence your child's health
Healthy humans have 26 pairs of chromosomes in every cell. Pairs are formed during conception, when egg and sperm cells come together. One chromosome comes from the mother and one from the father, making matched pairs totaling 46 chromosomes in all.
Variations in the matching process can have a major impact on a child's health. For example, babies born with an extra chromosome 21 usually have
Down syndrome, a condition that changes their facial features, muscle tone, learning abilities and more.
In other cases, children can inherit a gene that causes a specific illness.
Sickle cell disease is one example of single-gene conditions present at birth (often called congenital health conditions).
Possible benefits of prenatal genetic testing
Every child born with a genetic condition is different. Some have no serious health issues at all. Some have brain differences that affect learning and development. Others have body parts or systems that are formed differently and may not function well. In some cases, genetic disorders cause miscarriage or stillbirth.
Prenatal genetic testing supports parents by offering them the gift of time. Knowing beforehand that their child might be born with a serious health issue can help them cope with powerful emotions and seek much-needed support. It also helps parents make key decisions about their baby's care. Testing can even uncover serious conditions—such as a malfunctioning heart—that neonatal surgeons can treat before babies are born.
Health conditions prenatal genetic testing can reveal
The difference between screening & diagnostic tests
Prenatal genetic tests fall into 2 groups, based on what test results might show.
Screening tests use a sample of the pregnant parent's blood to look for elevated risks of genetic disorders. Findings might point to possible disorders, but do not confirm that your child has a specific condition.
Diagnostic tests go one step further by sampling fluid and tissues inside the womb to gain access to your baby's DNA. These tests can confirm a specific diagnosis.
Carrier screening before & during pregnancy
Biological parents can act as "carriers" for health conditions that run in families. Some parents carry these health risks without knowing it. Carrier screening reveals specific conditions they might pass along to their child.
Blood tests taken before pregnancy or early in pregnancy (6-10 weeks) can reveal single-gene conditions like sickle cell disease and cystic fibrosis. Both parents should be tested, since babies of two carrier parents may have a more serious form of the condition. Carrier screening is not required for future pregnancies, since the results will be noted in each parent's medical records.
Screening tests offered in the first trimester
These tests can be performed after the first 11 weeks of pregnancy:
Cell-free fetal DNA testing, also known as non-invasive prenatal testing (NIPT), analyzes small bits of a baby's DNA found in the pregnant parent's blood. This can uncover signs of an extra, missing or damaged chromosome that might cause serious health outcomes.
Serum screening also uses a blood sample. Instead of searching for snippets of the baby's DNA, though, it measures proteins in the pregnant parent's blood that signal chromosomal differences.
Nuchal translucency (NT) uses ultrasound to measure the thickness of the back of a baby's neck. This can point to abnormal chromosome counts and physical issues such as a malformed heart.
Sequential screening, which pairs serum testing in the first and second trimester with NT, can also detect an extra or missing chromosome.
Screening tests offered in the second trimester of pregnancy
AFP screening, also called maternal serum screening, measures the level of alpha-fetoprotein in the pregnant parent's blood. High levels of AFP may signal neural tube defects where the baby's spinal cord does not close completely (such as
spina bifida) or incomplete development of the brain (anencephaly). AFP screening can also detect
multiple pregnancies (like twins or triplets) or incorrect pregnancy dating (meaning you're earlier or later in the process than expected). This test is usually offered between 15 and 22 weeks of pregnancy.
Quad screening may also be offered in the 15-to-22-week window. This test looks for 4 different markers in the pregnant parent's blood that may point to Down syndrome, trisomy 18, or neural tube defects.
A
fetal anatomy scan uses ultrasound to look for differences in your baby's brain, bones, heart, kidneys, abdomen, face, arms and legs. This scan is usually offered around 20 weeks of pregnancy, sometimes as a follow-up to earlier blood screening.
Diagnostic tests to confirm genetic conditions
These prenatal tests are typically done after screening tests show warning signs of genetic differences, or when there are other reasons your child may face serious risks for genetic conditions.
Unlike screening tests, diagnostic tests can confirm a genetic diagnosis. But like all prenatal genetic tests, these tests are optional. Some parents choose not to have these invasive tests due to slight risks for bleeding, infection and miscarriage. Others feel the benefit of knowing their baby's diagnosis outweighs any possible dangers.
Diagnostic tests your health care team will offer you include:
Amniocentesis, which uses a needle inserted through your abdominal skin into your uterus to collect a sample of amniotic fluid for DNA analysis. This test can be done between 16 and 20 weeks of pregnancy.
Chorionic villus sampling (CVS), which uses a needle to collect a small sample of cells from the placenta, an organ inside the womb that nourishes and sends oxygen to your baby. Your care team will determine whether it's safest to insert the needle through your abdomen or vagina. This test is usually done around 11 to 13 weeks of pregnancy.
Some diagnostic test results may be ready after 72 hours, while others may take several weeks to complete.
Finding advice to help you decide
Prenatal genetic testing is a personal choice, but the process of deciding can cause confusion and stress. If you're unsure, talk with your health care team. Your OB-GYN or pediatrician can answer common questions about genetic testing—both the benefits and limitations. Parents can also meet with a
genetic counselor to review family risks and learn more about the value of genetic testing.
Questions to consider asking your health care team or genetic counselor
What screening tests do you recommend, based on my health history?
If screening tests come back positive, what happens next?
How accurate are the tests? What are the chances of false positives?
What are the possible concerns and risks if I opt out of testing?
Remember
Your health care team, which might include a genetic counselor, can help you make informed decisions about testing and your child's health.
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