What is the difference between Down syndrome screening and non-invasive prenatal testing?
Jul 19, 2025
Source: Cainiu Health
Dr. Zhang Lu
Introduction
The Down syndrome screening and non-invasive DNA testing generally differ in aspects such as testing principles and accuracy. Down syndrome screening calculates the risk of chromosomal abnormalities by measuring specific hormone levels in the pregnant woman's blood and combining this with information such as the mother's age and weight. Non-invasive DNA testing, on the other hand, involves collecting the pregnant woman's peripheral blood, extracting fetal cell-free DNA, and using gene sequencing technology to analyze chromosomal abnormalities.
"Non-invasive" refers to non-invasive prenatal DNA testing. Under normal circumstances, there are differences between Down syndrome screening and non-invasive DNA testing in terms of testing principles, accuracy, target population, detection scope, and risks. A detailed comparison is as follows:
1. Testing Principle: Down syndrome screening measures specific hormone levels in the pregnant woman's blood and calculates the risk of chromosomal abnormalities based on factors such as maternal age and weight. Non-invasive DNA testing analyzes fetal cell-free DNA extracted from maternal peripheral blood using genetic sequencing technology to detect chromosomal abnormalities.
2. Accuracy: The accuracy of Down syndrome screening is relatively lower, with a certain rate of both false positives and false negatives, potentially requiring further diagnostic testing for confirmation. Non-invasive DNA testing has a higher detection rate for common trisomies and a lower false positive rate.
3. Target Population: Down syndrome screening is more suitable as an initial screening method for average-risk pregnant women, especially those under 35 years of age. Non-invasive DNA testing is recommended for women with high-risk results from serum screening or those who have missed the optimal time window for Down syndrome screening.
4. Scope of Detection: Down syndrome screening primarily assesses the risk of trisomy 21, trisomy 18, and open neural tube defects. Non-invasive DNA testing can detect common trisomies including trisomy 21, 18, and 13, and in some cases, can also identify other chromosomal abnormalities.
5. Risks: Down syndrome screening involves a blood draw and is non-invasive, but due to its limited accuracy, it may lead to an increased likelihood of follow-up invasive diagnostic testing. Non-invasive DNA testing requires only a sample of maternal peripheral blood, making it a non-invasive procedure with no risk to either the mother or the fetus.
When choosing between Down syndrome screening and non-invasive DNA testing, individuals should consider their personal circumstances and follow medical advice. If abnormal results are detected, timely further diagnostic evaluation is necessary to clarify the situation and take appropriate actions to ensure a healthy pregnancy.
