The Integrated Screening Test is a way to estimate the chance that a baby will be born with Down syndrome, trisomy 18, or an open neural tube defect.
The test uses measurements from two blood tests and from a first trimester ultrasound. All of this information is combined, or integrated, with other details about you to tell you more about your developing baby.
- The two blood tests measure proteins that are made by the developing baby and placenta. The first blood test is taken between the 11th and 13th week of your pregnancy, and the second is taken ideally between 15 and 18 weeks, although this can be measured up to the 21st week.
- An ultrasound is taken between the 11th and 13th week, to measure the baby’s length to confirm that you are in the right timeframe for the screening, and measure the fluid-filled space at the back of the baby’s neck, which is called the nuchal translucency.
If your test result is positive (abnormal)
Your doctor will likely refer you to a genetic counselor because you are considered to be at a high risk for having a baby with Down syndrome, trisomy 18, or an open neural tube defect. On average, one in about 30 women will have a positive Integrated Screening result. A positive result does not mean that your baby has one of these problems. Other factors may affect the test results. Your provider may suggest further testing such as a detailed ultrasound of the baby’s anatomy and/or an amniocentesis.
If your result is negative (normal)
If your Integrated Screening is negative, then you are considered to be at low risk to have a baby with Down syndrome, trisomy 18, or an open neural tube defect. Screening tests can not diagnose or rule out any specific condition, nor ensure the birth of a healthy baby.
About these conditions
Integrated Screening will help find 9 out of 10 babies with Down syndrome, 8 out of 10 babies with trisomy 18, and 8 out of 10 babies with open spina bifida.
- Down syndrome, also called trisomy 21, is a condition that causes mental retardation, heart defects, and other problems. Down syndrome is caused by an extra chromosome in the developing baby. Although the chances of having a baby with Down syndrome increase with the age of the mother, it can happen at any age. About one in 600 babies are born with Down syndrome.
- Trisomy 18 is caused by an extra chromosome in the developing baby. Few babies with trisomy 18 survive to birth. Trisomy 18 causes mental retardation, heart defects, very poor growth, and other problems. Just like with Down syndrome, the chances of having a baby with trisomy 18 increases with the age of the mother. One baby in 6000 is born with trisomy 18.
- A baby with an open neural tube defect (NTD) has an opening of the spine or of the head. The most common form of open NTD is called spina bifida, which happens when the spine does not close properly, exposing the spinal cord, which may become damaged. One baby out of every 1000 is born with an open NTD.
Want to Know More?
- Dartmouth-Hitchcock Obstetrics
- National Down Syndrome Society