NIPT test for high risk of Down syndrome, does the fetus have the disease?

NIPT is a non-invasive prenatal screening test that analyzes free DNA fragments of the placenta circulating in the mother’s blood to detect abnormalities in the number of chromosomes such as Down syndrome (Trisomy 21), Edwards (Trisomy 18), Patau (Trisomy 13)…

The appropriate time to perform NIPT is the 9-10th week of pregnancy, when the percentage of fetal DNA in the mother’s blood has reached the standard level for testing (over 4%). However, to achieve optimal results, pregnant women should perform NIPT after ultrasound to measure nuchal translucency at weeks 11-13.

NIPT is a highly accurate screening method that can detect 99.7% of Down syndrome, with a very low false positive rate of 0.04%. However, this is only a screening test, not a diagnostic test, and does not replace ultrasound screening for fetal structural defects and specialized genetic diagnostic procedures.

At week 11, the sonographer evaluates the anatomical structures of the fetus and measures nuchal translucency (NT). Many cases of Down syndrome still have NT index within normal limits, and more than 50% do not have any structural abnormalities of the fetus noted on ultrasound. Therefore, NIPT has very important value in screening for common aneuploidies, especially Down syndrome.

On the contrary, ultrasound can detect morphological abnormalities or very thick nuchal translucency over 3.5 mm, suggesting many genetic abnormalities other than Down syndrome. Therefore, ultrasound should be performed first to guide NIPT and diagnostic tests.

When NIPT results are high risk, pregnant women may be advised to undergo definitive diagnostic testing including chorionic villus biopsy from week 13 or amniocentesis at week 16 to analyze fetal cells. In addition, early detailed fetal ultrasound is important to screen for structural defects that appear early in pregnancy.

In case you are in the 11th week of pregnancy, you should not panic too much as it will affect your health. You should go to a medical facility specializing in Fetal Medicine and bring NIPT results to receive genetic counseling as soon as possible. The doctor will comprehensively evaluate detailed NIPT parameters, perform an in-depth ultrasound to check the condition of the mother and fetus, and come up with an appropriate and safe treatment plan for you.