Iowa Integrated Screen
The Iowa Integrated Screen is a prenatal screen that combines or “integrates” information from an early ultrasound and two blood tests to give your chance of having a baby with Down syndrome, Trisomy 18 or an open neural tube defect in the current pregnancy. The Iowa Integrated Screen is performed in two stages. Stage One is performed in the first trimester. Stage Two is performed in the second trimester between 15 and 20 weeks of pregnancy.
Stage One involves:
- Performing an ultrasound to measure the fetus and accurately determine the gestational age of the pregnancy. The nuchal translucency (NT) may also be measured if the ultrasound is being done by an NT-certified sonographer. The nuchal translucency is a collection of fluid behind the fetal neck that can be seen in any fetus in the first trimester of pregnancy. Having an NT measurement done improves the performance of the Iowa Integrated Screen.
- Taking a blood sample to measure the concentration of pregnancy associated plasma protein-A (PAPP-A). This is usually drawn after the ultrasound and is often drawn on the same day.
Stage Two involves:
- Taking a second blood sample to measure the concentration of alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), and unconjugated estriol (uE3).
- Integrating the measurements of the markers in your blood from both stages, together with your age and the NT measurement, if available. If an NT measurement was not done, integrating the results of the two blood tests is still an effective screen for Down syndrome, Trisomy 18 and open neural tube defects.
- Notifying your healthcare provider of this Integrated Screening result after the ultrasound and both blood tests are completed.
All of the blood markers are made by the developing baby and the placenta. The levels of these markers may be altered in a predictable way when a developing baby has a chromosome problem such as Down syndrome or Trisomy 18, or certain birth defects such as an open neural tube defect.
- In pregnancies with Down syndrome, the levels of PAPP-A, AFP, and uE3 tend to be lower and the nuchal translucency (NT) measurement and hCG tend to be higher than average.
- In pregnancies with Trisomy 18, the levels of PAPP-A, AFP, uE3, and hCG tend to be lower and the NT measurement tends to be higher than average.
- In pregnancies with an open neural tube defect, the level of AFP is usually increased. If the defect is in the spinal cord itself, but is covered by skin, AFP will not leak into the amniotic fluid and so the AFP level may not be increased. These defects will not be detected by the blood test and the effects tend to be less severe.
Any woman can have a baby with Down syndrome or Trisomy 18, but it is known that these and other chromosome abnormalities are more likely to occur as women get older. This is why the Iowa Integrated Screen includes maternal age in the risk calculation. This means that as a woman gets older she is more likely to have a result that is screen-positive (higher risk) and so be offered a diagnostic test. The chance of having a baby with an open neural tube defect does not increase with a woman’s age.
Integrated Test Technology under license from Intema Ltd, UK