NIPS is a screening test to determine if a pregnancy may be at an increased risk for a particular condition, so the family may decide if they would like
to pursue further testing during their pregnancy.
It looks at small pieces of chromosome material released by the placenta into the mother’s blood stream. This test screens chromosomes 21, 18, 13, X and
Y for extra or missing copies. The most common conditions screened for are trisomy 21 (Down syndrome), trisomy 18, trisomy 13, Turner syndrome (monosomy
X), Klinefelter syndrome (XXY), and triple X syndrome.
This test will either come back with an increased risk for one of these conditions, or will come back with a decreased risk for all conditions screened
for, which is a risk of 1 in 10,000. This screening test can detect approximately 99.2% of cases of Down syndrome, and over 95% of cases of trisomy
18 and 13. However, it is just a screening test and cannot diagnose or rule out any of these conditions in a pregnancy.
Expanded NIPS refers to NIPS screening tests that look for abnormalities in chromosomes other than 21, 18, 13, X and Y.
The accuracy of looking for conditions beyond the standard panel drops significantly. However, it may be useful in a situation where there are differences on an ultrasound that are suggestive of a genetic condition and the mother declines diagnostic testing such as an amniocentesis.
One of the things an expanded NIPS test may look for are microdeletions or small missing pieces of chromosomes. Most of these conditions have a positive predictive value of less than 1%. This means that even if you tested “positive” for a microdeletion on NIPS, your risk may be less than 1% to actually have a child with that condition.
NIPS is a rapidly growing field. However, the accuracy of these new platforms is not yet well understood. Therefore, it is currently recommended that women interested in pursuing NIPS for screening early in pregnancy have the traditional NIPS panel.
Not necessarily. Most companies use very similar technologies for NIPS. Your genetic counselor or health care provider can help determine if one particular company is preferable based on your specific needs. However, for traditional NIPS most companies are equal in accuracy.
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.
NIPS has detected a small number of cases of maternal cancer during pregnancy. However, these results look very different from a standard positive NIPS result. Often, these results come back positive for many chromosome conditions, giving both the laboratory and the genetic counselor an idea that something beyond the pregnancy may be going on. For example, these results will often say a baby has trisomy 18 AND monosomy 13, while the baby looks perfectly healthy on ultrasound. If you have had a positive NIPS result that turned out to be a false positive, you should not worry about an increased risk for cancer. Fortunately, most laboratories now can tell when an NIPS result is indicating the possibility of maternal cancer, and this would be discussed with you along with your results.
