About prenatal tests
Below are some of the most common tests, but you may be offered other tests than the ones listed here. Guidelines for prenatal tests are not the same in every region.
Check with your physician to see which prenatal tests are right for you and when they should be done.
There are 2 kinds of tests: screening tests and diagnostic tests.
Screening tests can detect risks of certain birth defects. They cannot tell you for sure if your baby has a problem. If your screening test shows a higher risk, you may have to decide if you want to follow up with a diagnostic test.
|Test||What is it?||What the test screens for||Follow up|
|Genetic carrier tests||Blood test offered to people with certain ethnic backgrounds. Usually done in the first trimester.||Genetic disease carriers. For example: cystic fibrosis, Tay-Sachs, or sickle cell anemia.||If the results show that you're a carrier, the father of the baby also needs to be tested.|
|Serum integrated screening||Uses 2 separate blood tests to measure pregnancy-related proteins. The first blood test is done between 10 weeks and 13 weeks 6 days. The second blood test is done between 15 and 20 weeks.||Down syndrome, trisomy 18, open neural tube defects, abdominal wall defects, and Smith-Lemli-Opitz syndrome. Detection rates vary depending on the birth defect.||If the result shows a high risk for one of these problems, you will meet with a genetic counselor. Further testing will be offered.|
|Full Integrated Screening||Uses same blood tests as Serum Integrated Screening and a nuchal translucency (NT) ultrasound. The NT ultrasound is done between 11 weeks, 2 days and 14 weeks, 2 days.||Down syndrome, trisomy 18, open neural tube defects, abdominal wall defects, and Smith-Lemli-Opitz syndrome. Detection rates vary depending on the birth defect.||If the result shows a high risk for one of these problems, you will meet with a genetic counselor. Further testing will be offered.|
|Non-invasive prenatal testing (NIPT)||Uses a blood test from as early as 10 weeks that looks at fetal DNA in the mother's blood. This test is only offered to women at high-risk such as advanced maternal age.||Down syndrome, trisomy 18 and trisomy 13.||If the result shows a high risk for one of these problems, you will meet with a genetic counselor. Further testing will be offered.|
|Alpha-fetoprotein||Blood test offered to women who have already had chorionic villus sampling or NIPT. Done between 15 to 20 weeks.||Open spine or abdominal defects. Detects 80 percent of spina bifida and 85 percent of abdominal defects. It may miss some babies with these defects.|
|Maternal serum quadruple screening||Blood test offered if you did not have the first trimester screen or chorionic villus sampling. Done between 15 to 20 weeks. Also called the quad test or expanded AFP screening.||Open neural tube defects (including spina bifida), abdominal wall defects, Down syndrome, trisomy 18, and Smith-Lemli-Opitz syndrome. Detection rates vary depending on the defect.|
|Ultrasound||Sound waves give you a snapshot of your baby and the surrounding area. Ultrasounds can be done at any point during pregnancy, but screening ultrasounds are usually done between 18 and 20 weeks. Also called a sonogram.||Some types of birth defects, including some that may be related to genetic disorders, such as Down syndrome. It may miss some babies with these disorders.||If the result of the screening ultrasound suggests an abnormality, further testing will be offered.|
Diagnostic tests can tell you if your baby actually has a specific birth defect. If the results of a screening test indicate an increased risk, your doctor may offer a diagnostic test. Diagnostic testing is available to all women (whether a screening test indicates an increased risk or not).
|Test||What is it?||What the test shows||Risk|
|Chorionic Villus Sampling (CVS)||Using ultrasound as a guide, your doctor inserts a small flexible tube through the vagina or a needle through the abdomen and removes a tiny piece of the placenta. Done between 10 to 14 weeks.||Down syndrome and other chromosomal problems. Can identify some genetic conditions.||Less than 1 in 300 chance of miscarriage.|
|Amniocentesis||Using ultrasound as a guide, your doctor inserts a thin needle through the abdomen to remove a small amount of the fluid around the baby. Done between 15 to 20 weeks.||Down syndrome and other chromosomal problems. Can identify some genetic conditions. Also tests for open spine and abdominal defects.||Between 1 in 300 and 1 in 500 chance of procedure-related miscarriage. Early amniocentesis is available in some areas; it has a slightly higher risk of miscarriage (about 1 percent).|