No. The sensitivity and specificity refer to the ability of the test to accurately call a negative result negative, or a positive result positive. If you’re screening result is “positive” (remember, this is not a diagnosis), the risk is based on your age and the specific condition. This is because the risk for many of the conditions screened for by NIPS increases each year as a woman ages. So as a woman ages, it is more likely for a positive to be a true positive.
For example, a 21-year-old woman who has a “positive” NIPS for trisomy 13 actually has just a 6% risk that the pregnancy is actually affected. This is because trisomy 13 is a rare condition, NIPS is not as accurate for trisomy 13 as other conditions, and because of her age, her starting risk was very low.
A 35-year-old woman who has a “positive” NIPS for Down syndrome however, has a 79% chance that the condition is actually present, because her starting risk based on her age was higher, NIPS is most accurate at screening for Down syndrome, and Down syndrome is more common in the general population.
Standard NIPS only screens for Down syndrome (trisomy 21), trisomy 13, trisomy 18, Turner syndrome (monosomy X), Klinefelter syndrome (XXY), and other possible sex chromosome differences. Most birth defects are not caused by these conditions. Therefore, a negative NIPS cannot identify your risk for other birth defects or genetic conditions.
Yes. Women who have undergone an organ transplant are not good candidates for NIPS. This is because small pieces of the organ donor’s DNA will be screened with the pieces of fetal DNA, giving an inaccurate result. Additionally, women who are currently affected with cancer should not undergo NIPS, since cancer cells often have chromosome differences that may lead to a false positive NIPS result. Finally, women on blood thinners such as Lovanox or Heparin are significantly more likely to have a non-reportable result, and should consider other screening options.
Most insurance companies will cover NIPS for a woman of any age as it is the recommended test for all women interested in screening during pregnancy. However, some insurance companies deny all genetic screening and testing as an exclusion in their policy. If your testing is denied by insurance most NIPS companies will allow you to pay a reduced rate that can range from $100-$350 depending on the company. Ask your provider what company they use and what specific billing policy that company has to determine your exact price.
Unfortunately, no. While the risk for Down syndrome, trisomy 18, trisomy 13, Turner syndrome, and Klinefelter syndrome drops to 1 in 10,000 with a “negative” NIPS result, this risk is not 0. While false negatives are rare, they do occur.
NIPS analyzes fetal DNA in the mother’s blood. The amount of fetal DNA in the samples is known as the fetal fraction. NIPS is only accurate at or after 10 weeks gestation because this is when there is a high enough fetal fraction to do the analysis. If the test cannot detect enough fetal material, a non-reportable result will be issued. This is also known as a low fetal fraction. Non-reportable results and results with low fetal fractions (below 3%) have been associated with a higher risk for a chromosome condition in that pregnancy. Women with these results should consider meeting with a genetic counselor to discuss the option of further screening (like a level II ultrasound) or repeating their NIPS later in pregnancy?
Yes. In over 95% of cases of Down syndrome there is no family history of this condition. The same can be said for trisomy 13, trisomy 18, Turner syndrome, and Klinefelter syndrome. Therefore, not having a family history of one of these conditions does not decrease your risk for these conditions below your age related risk in pregnancy.
Similarly, having just one affected relative with one of these conditions does not significantly increase your risk, since that condition was likely new to that person in your family and not inherited. However, having two or more relatives with same chromosome condition may imply an increased risk for that condition.
A screening test (NIPS, first trimester screening, maternal serum screening) adjusts a woman’s risk to have a pregnancy affected with a specific condition based on certain factors. The result will either increase or decrease the risk for those specific conditions.
A diagnostic test looks directly at the baby’s genetic information to give a yes or no answer as to whether or not a baby is affected by a specific condition. A diagnostic test is the only way to know for sure whether or not a baby is affected during a pregnancy. However, starting with a screening test may help a woman decide if a diagnostic test during a pregnancy is necessary.
No! Fetal sex or gender, just like every other part of NIPS, is considered a screening test. While this is by far the most accurate part of NIPS, false results do occur. If you do receive an incorrect fetal sex prediction through NIPS, which is usually noticed at your 20 week ultrasound, do not panic. This does not necessarily mean anything is wrong with the baby. There are many reasons NIPS can predict the incorrect fetal sex or gender.
Yes! However, it is important to note if you have a fraternal twin pregnancy (where the babies each have their own placenta and amniotic sac) the results are less accurate than when used in screening a singleton pregnancy. This is because each twin’s placenta may not release the same amount of chromosome material into the mother’s bloodstream, leading to one twin being either underrepresented or overrepresented. Therefore, for twins, the risk is not reduced as much with a negative NIPS as it would be in a singleton pregnancy. However, NIPS is still the most accurate blood screening test we have for twin pregnancies for these conditions.
