How does NIPS differ from first trimester screening?

Both are screening tests that assess the risk for Down syndrome and trisomy 18 in pregnancy by looking at a sample of a mother’s blood.

First trimester screening measures the levels of two proteins in the mother’s blood (PAPP-A and hCG) and combines those results with a 12 week ultrasound to look at a measurement on the back of baby’s neck called the nuchal translucency. Combining these numbers provides a risk for the pregnancy to have Down syndrome or trisomy 18.

NIPS looks at small pieces of chromosome material released by the placenta into the mother’s blood stream. No ultrasound is included for the risk analysis. NIPS additionally screens for trisomy 13 and sex chromosome (X and Y) differences in a pregnancy, as well as fetal sex. NIPS is also more accurate at screening for Down syndrome and trisomy 18 than first trimester screening. However, a nuchal translucency scan (part of the first trimester screen) can detect other concerns such as an increased risk for a baby to have a heart defect.

It is important to remember both tests are just screening tests and neither can diagnose or rule out a condition in pregnancy.