Genetic screening tests for women aged 35 and older

If you are 35 or older, you probably know that you are at a higher risk of pregnancy problems. To address any concerns, the doctor may suggest additional prenatal tests. It is up to you to decide if you want to take these tests.

Remember that most healthy women between the ages of 35 and 40 have healthy pregnancies and healthy children. But there are several ways that genetic testing can help manage a pregnancy:

You will gain peace of mind about your child's health.
You can learn about your child's special needs and prepare for them if a genetic problem is discovered.
You can use this information to help make decisions about how best to take care of your pregnancy.

Not all tests are safe, and sometimes tests can give false results. Talk to your doctor about the risks, benefits, and limitations of each test so you can make the best decision for you. Here is an overview of the tests that may be offered to you.

Ultrasound

Moms of all ages usually have one or more ultrasounds during pregnancy. This safe test uses high frequency sound waves to produce an image of your baby. With ultrasound, you can:

Confirm that you are pregnant
See if you are carrying more than one baby
Determine whether your baby's heart is beating
See if you are carrying more than one baby
Estimate your baby's due date and see how your baby is growing
Determine the baby's gender
Examine your ovaries and uterus
Determine the location of the placenta and the amount of amniotic fluid around your baby
Look for signs of birth defects such as cleft lip, heart defects, spina bifida, and Down syndrome

First trimester screen

This test is done between 11 and 14 weeks. It includes a blood test and an ultrasound.

The blood test measures two markers in the blood.
An ultrasound measures the thickness of your baby's neck.

Collectively, the results reveal problems with your baby's chromosomes, such as Down's syndrome.

This test performs the same function as the quad marker screen but allows the doctor to see your baby. It also tends to cause fewer false positives. It is sometimes combined with a second blood test, such as a quadruple screen, to give a more accurate result than any of the individual tests.

Quad marker screen

Quad marker screening is a blood test that is done between the 15th and 20th weeks of pregnancy. It measures substances in the blood that can show:

Problems with the baby's brain and spinal cord, called neural tube defects. These include spina bifida and anencephaly. The quad marker can detect approximately 75% to 80% of neural tube defects.
Genetic disorders such as Down syndrome. The test can detect about 75% of Down syndrome cases in women under 35 and more than 80% of Down syndrome cases in women 35 and older.

It's important to know that the quad marker screen only shows your risk level for birth defects. If the test shows a higher risk than the average risk for a 35-year-old woman, then the test is considered positive. The test cannot diagnose birth defects, so a positive result does not mean your baby has a birth defect. In most cases, the child is healthy despite an abnormal test result.

If the test is positive, your doctor may suggest that you undergo diagnostic tests such as:

Amniocentesis to check your baby’s chromosomes
Ultrasound to look for signs of birth defects

Amniocentesis

Unlike blood tests, which only show if you are at risk, amniocentesis is used to make a diagnosis. During the test, your doctor will insert a needle through the wall of your abdomen, using ultrasound images to help guide the needle into your uterus. They will remove a small amount of amniotic fluid from the sac surrounding your baby. This sample is then used to check the baby's chromosomes and test for genetic diseases. In addition to the most common chromosomal problems, including Down syndrome, trisomy 18, trisomy 13, and Turner syndrome, the sample can be tested for:

Sickle cell disease
Cystic fibrosis
Muscular dystrophy
Tay-Sachs disease
Neural tube defects, such as spina bifida and anencephaly

Chorionic villus sampling

Chorionic villus sampling is an alternative to amniocentesis and can be done early in pregnancy. Like amniocentesis, chorionic villus sampling can diagnose certain medical conditions. If you have certain risk factors, you may be offered a chorionic villus biopsy to check for birth defects in early pregnancy.

During this test, a small sample of cells called chorionic villi is removed from the placenta. Chorionic villi are tiny parts of the placenta that form from a fertilized egg, so they share the same genes as your baby. To obtain cells, the doctor inserts a needle through the vagina or abdomen, depending on the location of the placenta. The cells are used to check your baby's chromosomes, similar to an amniocentesis.

Chorionic villus sampling and amniocentesis usually include genetic counseling when you talk to a counselor about the risk of genetic diseases. You will also learn about the risks and benefits of the procedures. When carrying twins, a chorionic villus sampling is usually not performed due to the risks.

Non-invasive prenatal diagnosis

This new blood test, also called a cell-free DNA test, is used to determine if you are at risk of having a baby with chromosomal problems. Because it is done using a sample of your blood, it is less invasive than amniocentesis or chorionic villus sampling.

The test is carried out between 10 and 22 weeks of pregnancy. It finds your baby's DNA floating in your blood. The result determines the likelihood of your baby being born with Down syndrome, trisomy 18, or trisomy 13.

Non-invasive prenatal diagnosis detects about 99% of cases of trisomy 21 and trisomy 18, which is much better than other blood tests. Most cases of trisomy 13 can also be detected with this test.

If the test shows an increased risk of chromosomal problems, your doctor may recommend a chorionic villus sampling or amniocentesis to confirm the diagnosis.

Since this is a new test, not all insurers cover it. Check with your insurance company to see if the cost of the test will be covered.