Integrated Screening

Integrated Screening is the official test offered to all pregnant California women by the California Genetics Disease Screening Program. It screens for risk of chromosomal problems, such as Down syndrome and trisomy 18, as well as neural tube defects. Neural tube defects are defects of the spinal column and brain, such as spina bifida where the spine (backbone) doesn’t form properly around the spinal cord, or anencephaly where part of the brain and skull are missing.

Pregnant woman having ultrasound test

Integrated screening is called “integrated” because it combines two blood tests and sometimes a special ultrasound exam. All the tests are non-invasive and pose no risk of miscarriage.

The first blood test is done between 10 weeks and 13 weeks, 6 days of your pregnancy. It measures the amount of pregnancy associated plasma protein-A (PAPP-A) in your blood. The second blood test is done between 15 and 16 weeks of your pregnancy. It is often referred to as Quad Marker Screening and measures four pregnancy hormones in your blood:

Alpha-fetoprotein (AFP) – a protein produced by the baby that crosses the placenta into your bloodsteam
Human chorionic gonadotropin (hCG) – a hormone produced in the placenta
Inhibin A (IhA) – a hormone released by the placenta
Unconjugated estriol (uE3) – a type of estrogen produced by the baby and the placenta

Frequently, a special ultrasound exam is added to the two blood tests to make the integrated screening results more accurate. The ultrasound portion of integrated screening is done between 11 weeks and 2 days to 14 weeks and 2 days of pregnancy. It confirms the dates of your pregnancy by measuring your baby’s size and proportions, and also measures your baby's "nuchal translucency" (NT), the thickness of the fluid buildup at the back of the developing baby's neck. If this area is thicker than normal, it can be an early sign of Down syndrome, trisomy 18 or heart problems. (Learn more about nuchal translucency testing.)

Compared with other screening tests, such as the Quad Marker Screening by itself, integrated screening offers a high detection rate for Down syndrome and has a low false-positive rate. About 9 out of 10 cases of Down syndrome are detected by integrated screening (about a 92 percent detection rate). However, it is not a “diagnostic” test that can tell you if your baby actually has Down syndrome, trisomy 18, neural tube defects, or other birth defects.

Understanding Results

Most women receive a preliminary result that includes the first-trimester blood test and the NT measurement once both those tests are complete. A final result that includes all three tests is typically available about one to two weeks after the second-trimester blood draw.

About 5 percent of all women who have Integrated Screening will get a result that says they are “screen positive.” The majority of them will have healthy babies. To use the example of Down syndrome, you will receive a screen positive if the risk for Down syndrome is one in 270 or higher.

If you receive a “screen positive” result, you will receive genetic counseling and will have the choice to get further testing, such as amniocentesis.

If you receive a “screen negative” result, it does not mean that you can rule out having a baby with birth defects. It does, however, mean that your risk is lower. You will receive an individualized personal risk estimate as a fraction. The larger the number on the bottom of the fraction is, the lower your risk. For example a 1/500 chance for Down syndrome is lower than a 1/300 chance.

Missing a Test

Because the first blood draw must be done between 10 weeks to 13 weeks, 6 days of pregnancy, women who realized they were pregnant when they were further along or did not see a doctor during the first trimester may miss the first blood test. If this applies to you, you can still have the Quad Marker Screening, but this test will not be part of an Integrated Screening Test.

Some women elect to skip the NT ultrasound. In this case, you will have a Serum Integrated Screening, which means your results will be based on just your two blood tests.

If you do not have the second blood test between 15 and 20 weeks of pregnancy, you will only receive results for the first stage of testing. This is less accurate than integrated screening.

Accuracy of Testing

Full integrated screening has the highest accuracy in detecting increased risk of birth defects. In general, all three tests (two blood tests and the NT ultrasound) combine for an accuracy of: