Can non-invasive DNA testing replace NT screening?

Feb 26, 2025 Source: Cainiu Health

Dr. Zhang Lu

Introduction

Under normal circumstances, non-invasive DNA testing cannot replace NT (nuchal translucency) screening. Although both non-invasive DNA testing and NT screening can assess, to some extent, the risk of fetal chromosomal abnormalities, non-invasive DNA testing primarily focuses on detecting chromosomal abnormalities, while NT screening emphasizes the evaluation of fetal structural and developmental abnormalities.

Generally, non-invasive DNA testing cannot replace NT screening. Pregnant women are advised to undergo both NT screening and non-invasive DNA testing according to their doctor's recommendations during pregnancy, to comprehensively assess the health status of the fetus. The analysis is as follows:

Non-invasive DNA testing analyzes fetal free DNA in the mother's peripheral blood to assess the risk of fetal chromosomal abnormalities. This test is non-invasive and requires only a blood sample from the pregnant woman, which is then analyzed using advanced biotechnology. NT screening evaluates the risk of chromosomal abnormalities such as Down syndrome by measuring the thickness of the nuchal translucency in the fetus via ultrasound imaging.

Non-invasive DNA testing primarily focuses on detecting chromosomal abnormalities, such as trisomy 13, trisomy 18, and trisomy 21, and has a high accuracy rate in predicting genetic disorders like Down syndrome. NT screening is usually performed between 11 and 13+6 weeks of pregnancy. In addition to assessing the risk of chromosomal abnormalities, it can also evaluate more obvious fetal organ malformations, such as anencephaly, single ventricle heart, and open spina bifida—conditions that non-invasive DNA testing cannot detect.

Although both non-invasive DNA testing and NT screening can assess to some extent the risk of fetal chromosomal abnormalities, non-invasive DNA testing mainly focuses on detecting chromosomal abnormalities, while NT screening emphasizes the evaluation of fetal structural and developmental anomalies. Therefore, non-invasive DNA testing cannot fully replace NT screening.

If the test results are abnormal, further prenatal diagnostic procedures, such as amniocentesis or chorionic villus sampling, are required to confirm whether the fetus has chromosomal abnormalities.

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What time should you stop eating the night before a non-invasive procedure?

Most non-invasive tests (such as non-invasive DNA testing and certain imaging examinations) require fasting to avoid substances produced during digestion from affecting the accuracy of test results. Stop eating after 8 p.m. the night before the test; by the time of the examination the next day (typically after a 10–12 hour interval), the gastrointestinal tract will have largely emptied, minimizing interference with test measurements.

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How many weeks into pregnancy can you have an ultrasound?

In general, it is usually recommended to have the first ultrasound between 6 to 8 weeks of pregnancy, with subsequent scans scheduled according to the individual's pregnancy progress and as advised by the doctor. The optimal time for the initial ultrasound after conception is 6 to 8 weeks, although the exact timing should be determined based on menstrual cycle and physical symptoms, with a personalized examination plan established by a healthcare provider. Avoid scheduling scans earlier than necessary due to excessive anxiety, but also ensure that no essential examinations are missed.

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What to do if the Down syndrome screening result is high risk

For a high-risk result from Down syndrome screening, further diagnostic tests are generally required to confirm the diagnosis, including consultation with a specialist to understand the situation and maintaining emotional stability to avoid anxiety. Options such as amniocentesis or non-invasive DNA testing may be chosen. These tests can more accurately determine whether the fetus has chromosomal abnormalities, providing a basis for subsequent decision-making and preventing unnecessary actions based solely on the high-risk screening result.