When To Do Genetic Testing During Pregnancy

Who Should Get Genetic Testing

The decision to get prenatal genetic testing is a personal choice. Ask your healthcare provider what they recommend if youre unsure. The results provide important information about the health of the fetus. Healthcare providers offer all pregnant families genetic screening as part of their pregnancy care.

Some of the reasons families will choose diagnostic genetic testing during pregnancy are:

• Irregular result of a genetic screening test.
• Family or personal history of genetic conditions.

Types Of Genetic Tests

Here are some common types of genetic tests:

• Carrier screening. This test is a simple blood test that both parents can take to check if either carries specific genes for certain hereditary disorders such as Tay-Sachs disease, sickle cell disease, and cystic fibrosis, among others. The screening is usually done before you get pregnant, but it can also be done while youâre pregnant.

• Screening tests for neural tube defects or chromosomal disorders. These tests are done at different times during your pregnancy and help your healthcare provider assess the risk that your baby will have a neural tube defect or a chromosomal disorder . Screening tests are offered to all pregnant women and may involve a blood test, an ultrasound, or both. These tests do not put your unborn baby at risk.

• Diagnostic tests. These tests are usually recommended if a screening test result indicates your baby may be at a higher risk of certain genetic conditions. The tests are done on cells taken from your uterus. The cells are analyzed in order to form a diagnosis.

What Are My Options If My Test Results Indicate A High Risk For A Genetic Or Chromosome Disorders

Your doctor likely has a standard protocol if a screening shows a mom-to-be is at high risk for a chromosomal disorder, so he or she will know how to help you understand the next steps before you even get started.

When a prenatal screening indicates that your child is at risk for a genetic or chromosome disorder, your doctor may suggest a diagnostic test, such as an amnio or CVS, to diagnose the condition. If a diagnostic test yields a positive result, your doctor might refer you to a genetic counselor, who can talk you through all your options in more detail.

Your practitioner may recommend a specialized birth facility for labor and delivery that can better address your specific needs or recommend medical interventions which, if performed immediately after birth, can improve your babys quality of life.

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Group B Strep Culture

Group B streptococcus is a type of bacteria found in the lower genital tract of about 20 percent of all women. While a GBS infection does not usually cause problems in women before pregnancy, it can cause serious illness in mothers during pregnancy. GBS may cause chorioamnionitis and postpartum infection. Urinary tract infections caused by GBS can lead to preterm labor and birth or pyelonephritis and sepsis.

GBS is the most common cause of life-threatening infections in newborns, including pneumonia and meningitis. Newborn babies contract the infection during pregnancy or from the mothers genital tract during labor and delivery.

The Centers for Disease Control and Prevention recommends screening all pregnant women for vaginal and rectal GBS colonization between 35 and 37 weeks gestation. The treatment of mothers with certain risk factors or positive cultures is important to reduce the risk of transmission of GBS to the baby. Babies whose mothers receive antibiotic treatment for a positive GBS test are 20 times less likely to develop the disease than those without treatment.

When Is Internal Fetal Monitoring Needed

On occasion, internal fetal monitoring is needed to provide a more accurate reading of the fetal heart rate. Your bag of waters must be broken and your cervix must be partially dilated to use internal monitoring. Internal fetal monitoring involves inserting an electrode through the dilated cervix and attaching the electrode to the scalp of the fetus.

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Prenatal Screening And Testing

Prenatal testing may be offered to women during pregnancy to determine if the fetus has apossibility to be born with a genetic condition or birth defect. Performing prenataltesting may be useful in determining different options for the pregnancy or specialmanagement of the pregnancy and delivery to improve the outlook for the baby. Severaltypes of prenatal testing are available, depending on which trimester of pregnancy themother is in and the type of condition in question. This appendix provides an overviewof different prenatal tests that may be offered to pregnant women.

Who Should Have Nipt/cfdna Screening

NIPT/cfDNA screening is available to all pregnant people. NIPT/cfDNA screening can be used as a second screen or as a first screening test . Ontario Health Insurance Plan will pay for NIPT/cfDNA screening for people in Ontario who meet certain criteria.

Have a positive prenatal screening result such as Enhanced First Trimester Screening or other conventional screening methods described in Table 1

Are over the age of 40 at the expected date of delivery

Have had a previous pregnancy or child with a chromosome condition

Have findings on ultrasound which are associated with an increased risk for Down syndrome, trisomy 18 or trisomy 13

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Talk To Your Provider About Which Prenatal Tests Are Right For You

What are prenatal tests and why are they important?

Prenatal tests are medical tests you get during pregnancy. They help your health care provider find out how you and your baby are doing.

You get some prenatal tests several times during pregnancy at your prenatal care checkups. These tests make sure you and your baby are staying healthy. There are other tests that are done at certain times during your pregnancy. These prenatal tests check to see if your baby has any health problems, including:

• Birth defects. These are health conditions that are present at birth. They change the shape or function of one or more parts of the body. Birth defects can cause problems in overall health, how the body develops or how the body works.
• Genetic and chromosomal conditions. These conditions are caused by changes in genes and chromosomes. A gene is part of your body’s cells that stores instructions for the way your body grows and works. A chromosome is the structure in cells that holds genes. Genetic conditions include cystic fibrosis , sickle cell disease and heart defects. A common chromosomal condition is Down syndrome. Sometimes these conditions are passed from parent to child, and sometimes they happen on their own.

What are screening tests and diagnostic tests?

Screening tests check to see if your baby is more likely to have a health condition, but they dont tell you for sure if you baby has a condition. There are no risks to you or your baby when you have a screening test.

What To Expect From The Prenatal Genetic Testing Procedure

Each type of prenatal genetic testing has a different process. For genetic screening, you may simply submit a family health history and undergo a blood test. For certain types of genetic testing, both partners may have a blood sample taken to determine if theyre carriers for certain conditions, such as sickle-cell anemia or cystic fibrosis. You may also opt for a paternity test before birth, which is more invasive for the fetus.

Each type of prenatal genetic testing has a different process. For genetic screening, for instance, you may simply submit a family health history and undergo a blood test.

During the screening process, your blood will be analyzed for certain genetic markers. Once the testing is complete, youll have a counseling session to discuss the results with your doctor. At this point, if the screening has indicated high risks of genetic abnormalities, then youll have options for diagnostic testing.

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What Is The Nt Measurement

• The nuchal translucency is a fluid filled space at the back of every babys neck
• A larger NT measurement is associated with an increased chance for chromosome disorders like Down syndrome and some other genetic and non-genetic issues like congenital heart defect
• An ultrasound to measure NT is performed between 11 and 14 weeks of pregnancy and should be done at a certifiedultrasound site. Your health care provider will tell you where an NT ultrasound can be obtained.
• An NT measurement of 3.5 mm or bigger is considered significant and would be a screen positive. A referral for genetic counselling will likely be offered.

Table 1 has an overview of the prenatal screening tests available in Ontario and how they compare to each other. Not all test options are available in all areas.

Enhanced First Trimester Screening is the most commonly offered prenatal screening test. Both screen for Down syndrome and trisomy 18. Results from eFTS are available earlier in pregnancy.

A woman who presents to her first prenatal visit at a later gestational age may be offered Multiple Marker Screening .

If you are expecting twins, prenatal screening is available but in general is not as accurate as for pregnancies with one baby. Also, not all screening options will be available for a twin pregnancy. Talk to your health care provider for more about screening in a twin pregnancy.

Additional Conditions Which May Be Screened For By Prenatal Screening:

Trisomy 13

Babies with trisomy 13 have an extra chromosome 13. In general between 1/8,000 and 1/15,000 of babies born has trisomy 13. The chance of having a child with trisomy 13 increases with a pregnant person/egg donors age. Every individual with trisomy 13 is different however each individual is expected to have both serious intellectual disabilities and congenital anomalies, including differences of the brain, heart, eyes and face. Most pregnancies with trisomy 13 will miscarry. About 5-10% of infants will survive the first year of life. There are some individuals who have lived to adulthood. For information on trisomy 13, visit Support Organization for Trisomy 18, 13 and Related Disorders website. See Additional Resources for more information about genetics.

Sex chromosome differences

• have a diagnostic test under any circumstance because of the small risk of miscarriage
• change the course of their pregnancy by choosing to end the pregnancy

Remember that most babies are born without an anomaly, however 1 in 25 babies in Canada is born with a difference at birth requiring medical intervention . Prenatal screening does not screen for all possible congenital anomalies. There is no cure for Down syndrome, trisomy 18 or open neural tube defect

3. How will this information affect my feelingsthroughout the pregnancy?

Would I pursue diagnostic testingin the event of a screen positive result?

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Pros And Cons Of Prenatal Genetic Screening

Not all genetic testing has to be done during pregnancy. If two partners both belong to an ethnic group with a higher risk of certain genetic disorders, then the couple may undergo a test to see if they carry certain genes. This is called a carrier screening. Many genetic conditions such as Tay-Sachs, sickle cell disease, and cystic fibrosis require that both parents be carriers of the gene or genes.

This information can affect family planning choices, including whether to have children or to undergo IVF with preimplantation genetic screening.

Couples who discover that their baby has a genetic defect are generally referred to a genetic counselor to help them understand the condition and their options.

Genetic screening in pregnancy can determine the risk for birth defects and genetic conditions, but an actual diagnostic test can tell for sure. Couples who discover that their baby has a genetic defect are generally referred to a genetic counselor to help them understand the condition and their options.

Is Genetic Testing Covered By Health Insurance

Some genetic testing may be included with your health insurance. Your coverage will depend on your policy and in some cases your risk factors, such as being over age 35, a history of genetic issues, or other reasons for testing as deemed necessary by your doctor. You can contact your health insurance provider for the specifics.

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Before Pregnancy: Genetic Carrier Screening Tests

If you have a gene for a disorder but donât have the condition yourself, youâre called a carrier. Genetic carrier screening tells you if you and your partner have these genes and, if so, the chances youâll pass them on to your children.

You can get the tests either before or during pregnancy, but theyâre most useful beforehand.

A doctor will take a sample of your blood or saliva for testing. The lab can look for genes for many types of disorders, but the more common ones are:

• Spinal muscular atrophy

People from some ethnic groups may be more likely to be carriers for some conditions, so ask your doctor if youâre in a high-risk category. Common groups that may want carrier testing include non-Hispanic whites , people of Eastern European Jewish descent , and those of African, Mediterranean, and Southeast Asian backgrounds .

Before Conceiving A Pregnancy There Are Many Things A Couple Can Do To Reduce The Chance Of Birth Defects And Genetic Disease

• Take Prenatal Vitamins with folic acid before getting pregnant. Additional information on preventing birth defects.
• Talk to a doctor about screening to determine if you are a carrier of a genetic disease. Early identification of genetic diseases can affect the treatment.
• Learn more about your family medical history on both the maternal and paternal sides of your family and your partners family. Write this information down and bring it to your doctor.
• If you have concerns that a medication, drug, or other exposure could affect your future children, contact the Texas Teratogen Information Service Genetic counselors are available to provide information.

Prenatal genetic testing is one way a woman can improve the chance to have a healthy baby. About 95% of women who have prenatal genetic testing receive good news from the testing laboratory. Some of the tests that can look at the genetic health of the baby include chorionic villus sampling , amniocentesis, ultrasound, and maternal blood testing. It is important to learn all you can about the specific procedure or test itself. It is also a good idea to know its purpose, risks, benefits, and limitations. Below is a description of these procedures.

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Gender Blood Test: Benefits Of Prenatal Genetic Testing Explained

Prenatal genetic tests may provide information to would-be parents about the chances of their fetus having genetic abnormalities. There are two main kinds of prenatal genetic testing:

Prenatal screening testing may identify the likelihood of your baby having defects at birth . These tests are:

• Prenatal screening for cell-free DNA
• A specific type of ultrasound

Health care providers usually perform a prenatal screening test during the first or second trimester. Screening tests dont definitively diagnose birth defects if the results of the test indicate an increased risk of a genetic disorder, additional diagnostic tests may be needed to confirm a diagnosis.

An early sex blood test is a non-invasive prenatal test during which a health care provider takes a blood sample to identify the sex of the fetus. This method analyzes the cell-free fetal DNA present in the blood during early pregnancy.

What Types Of Prenatal Screening Tests May Be Available

Screening tests dont diagnose genetic conditions, and an abnormal result doesnt mean the fetus has a condition. It means theres a higher risk for a genetic disorder. Your healthcare provider can help interpret results from genetic screening tests and explain the next steps. In some cases, they may recommend diagnostic testing.

Some examples of prenatal genetic screening tests are:

Carrier screening

Carrier screening is a blood test that pregnancy care providers may offer you and your partner. This type of testing can identify small changes in the genes that increase the risk that the fetus could inherit serious medical conditions. These are often called single-gene conditions. Examples include cystic fibrosis, sickle cell disease and spinal muscular atrophy. If your blood test shows youre a carrier for a genetic risk, your partner should also undergo screening. If both parents are carriers of the same genetic risk, the fetus could have a more severe form of the disease. You only need to complete carrier screening tests once in your lifetime.

Screening for an abnormal chromosome number

Chromosomes should be inherited in pairs one half of the pair from each parent. Sometimes, nature makes mistakes during fertilization, resulting in missing, or extra, parts of the chromosome pair. Examples include Down syndrome and Turners syndrome . These test results will be different for each pregnancy. Types of tests include:

Screening for physical abnormalities

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Diagnostic Genetic Testing During Pregnancy

Chorionic villi sampling A small sample of placental tissue is obtained either transcervically or transabdominally under ultrasound guidance between 11-13 weeks of gestation.

Amniocentesis A small sample of amniotic fluid is removed by placing a needle into the amniotic cavity under ultrasound guidance after 16 weeks gestation.

What Is Prenatal Screening

There are several different types of prenatal genetic screening tests. Which types are available to you depend on where you live and how far along you are in your pregnancy. If you choose to have genetic screening, your ultrasound and a blood sample or samples will be used to test for signs of certain conditions. These include genetic abnormalities and neural tube defects . The results of prenatal screening tests are not a diagnosis. They provide you with a likelihood that your baby has one of these conditions. There are both false positive and false negative results, so a positive screen does not mean your baby is affected. For proper diagnosis, you will need to undergo further evaluation, such as non-invasive prenatal testing , or invasive testing such as amniocentesis or chorionic villus sampling. These two invasive procedures can determine whether a disease is present or not, and not just the chance of it. Because they are invasive and require putting an instrument into the uterus to obtain fetal cells, there is a risk of pregnancy loss.

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