What Is the Combined First Screen?
The Combined First Test is a first trimester (11 weeks to 13 weeks and 6 days) screening test that assesses the risk of a baby being born with Down syndrome. The screening combines information from an ultrasound and a maternal serum analysis.

A specialized ultrasound examination is used to measure the nuchal translucency(NT) of the fetus. A nuchal translucency is the sonographic appearance of a collection of fluid under the skin behind the fetal neck in the first-trimester of pregnancy. Fetuses with chromosome abnormalities such as Down syndrome tend to have an increased nuchal translucency compared to those without chromosome abnormalities.

Maternal serum analysis:
The levels of two substances in the mother’s blood are examined:
• Pregnancy-Associated Plasma Protein-A (PAPP-A)
• Total beta-human chorionic gonadotropin (total ß-hCG)

In pregnancies with Down syndrome, the levels of PAPP-A tend to be lower than normal while the levels of total ß –hCG tend to be elevated. In pregnancies with Trisomy 18, the levels of the PAPP-A and total B-hCG tend to be lower than normal.

What Are The Advantages Of Having The Combined First Test?
Because the Combined First Test is performed in the first trimester, it provides results early enough so that Chorionic Villus Sampling (CVS) is available as a diagnostic testing option.

Does The Combined First Test Detect All Pregnancies With Down Syndrome?
The Combined First Screen will detect 85% of pregnancies affected with Down Syndrome.

  • What Does a Screen Negative Test Result Mean?
    • If the risk of Down syndrome is lower than 1 in 200, then the result is considered a screen negative result for Down syndrome.Although a screen negative test result means that the patient is not at high risk for having a baby with Down syndrome, a screen negative result does not completely rule out the possibility of a pregnancy with Down syndrome.

      Because first semester serum testing does not measure the risk of open neural tube defects (ONTDs), it is recommended that women who undergo the Combined First Test should consider a maternal serum AFP test at 16 weeks of pregnancy.

  • What Does a Screen Positive Result Mean?
    • A screen positive for the Combined First Test means that you have a risk greater than or equal to 1 in 200 of a Down syndrome pregnancy. About 1 in 20 women (5%) who take the Combined First Test receive a screen positive result.
  • What if a Pregnancy is More Than 14 Weeks Along?
    • The Quad Test may be performed between 15 and 22 weeks.