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.
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) and hCG in your blood. The second blood test is done between 15 and 20 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.