Originally published by Harvard Health.
What is the test?
Blood tests and fetal ultrasound tests for pregnant women check the levels of protein and hormones being produced by the fetus and examine how the fetus is forming. The levels of four different substances as well as early findings on ultrasound can enable doctors to identify pregnancies that are at a higher risk for birth defects such as Down syndrome or neural tube defects (brain and spinal cord problems). If the screening tests suggest problems, your doctor might recommend additional tests, such as amniocentesis or chorionic villus sampling, to confirm the findings.
How do I prepare for the test?
Before having this test done, you need to think carefully about what you would do with the results once you have them. The results of these screening tests cannot show for sure whether you have either a healthy fetus or one with a problem. They can only suggest which patients might want to go ahead with further testing.
Either amniocentesis or chorionic villus sampling is recommended after an abnormal triple screen. These additional tests have a small risk of miscarriage. Most people with an abnormal screening test decide to go ahead with amniocentesis.
You can see that the decision to have birth defect screening early in your pregnancy is an important decision. You should have a screening test done only if you think the information it offers would help you to make decisions about your pregnancy.
The batch of screening tests that can be used during the first trimester of pregnancy is known as the “combined test”.
The batch of screening tests that is collected in the second trimester is named the “quadruple test.”
If you combine first trimester tests and second trimester tests together, this is called the “integrated test.”
What happens when the test is performed?
Your doctor needs to weigh you on the day or days you have your blood drawn and ask when your last period began or what your expected due date is. The analysis of the results will take into account your weight and stage of pregnancy to determine whether the levels are normal.
For first trimester screening, your blood is drawn between the 9th and 13th weeks of pregnancy. The blood is tested for two protein and hormone levels: human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A). At the time of these tests, an ultrasound of the fetus is done to measure the thickness of the tissue at the back of the fetus’s neck.
For second trimester screening, your blood is drawn between your 15th and 20th weeks of pregnancy. The blood is tested for four protein and hormone levels: maternal serum alpha fetoprotein (MSAFP), unconjugated estriol (uE3), inhibin A, and human chorionic gonadotropin (hCG).
What risks are there from the test?
There are no risks from this test itself, but there are some risks from tests that might be recommended if the test result comes back abnormal. This test can be stressful for expectant parents. Several things can cause the test to come back as abnormal even when there are no real health problems. Confusing results can happen, for example, in twin pregnancies and when mistakes have been made in estimating the age of the pregnancy.
Must I do anything special after the test is over?
How long is it before the result of the test is known?
The test results are available to your doctor within two or three days.