What is Integrated Antenatal Screening?
Integrated antenatal screening requires two blood tests along with ultrasound measurements to evaluate your baby’s chance of being born with birth defects.
The first phase of testing takes place between weeks 10-13 of pregnancy and consists of a blood test to measure both the amount of pregnancy associated plasma protein-A (PAPP-A) and free Beta HCG and an ultrasound to measure nuchal translucency (NT).
Nuchal translucency measurement is a non-invasive method of evaluating the thickness of the fluid-filled space at the back of your baby’s neck. The test does not provide a definitive diagnosis, but a larger than normal space is associated with Down syndrome.
The second blood test takes place between weeks 15-18 and measures the following blood proteins: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin-A.
The results of the tests are combined to estimate your risk of having a baby with Down syndrome, spina bifida, Trisomy 13 and 18.
Who Should Have Integrated Antenatal Screening?
Integrated antenatal screening is available for all pregnant women, but is not required. Your obstetrician may recommend testing for women considered to be at risk for having a baby with certain birth defects or Down syndrome.
Factors that increase the risk of having a baby with Down syndrome:
- Advance maternal age – the chances of having a baby with Down syndrome increases with a mother’s age, starting around age 35
- Previously giving birth to a child with Down syndrome – women who already have a child with Down syndrome are at a higher risk of having a second child with Down syndrome
- Being a genetic carrier of Down syndrome – parents who carry the Translocation Trisomy 21 are at an increased risk of having a child with Down syndrome
Integrated antenatal screening can correctly identify 95 percent of Down syndrome cases, but false-positive and false-negative results do occur.
Parents should not consider positive integrated antenatal screening results a definitive diagnosis, but rather an indicator that additional testing may be warranted.