How is the Down syndrome screening performed?
Jul 21, 2025
Source: Cainiu Health
Dr. Zhang Lu
Introduction
Under normal circumstances, the process of Down syndrome screening mainly includes the following steps: determining the timing of the examination, preparing before the test, sample collection, testing and calculating the risk value, obtaining and interpreting the report. When undergoing Down syndrome screening, it is important to stay relaxed and avoid excessive anxiety. After the examination, maintain a balanced diet, ensure adequate rest, and follow the doctor's recommendations for regular prenatal checkups.
Generally, the process of Down syndrome screening mainly includes determining the examination time, preparation before the test, sample collection, testing and risk value calculation, and obtaining and interpreting the report. The details are as follows:
1. Determine the examination time: Down syndrome screening must be performed at a specific gestational week, with the optimal time being between 15 and 20 weeks of pregnancy. During this period, fetal-related indicators are relatively stable, and the accuracy of results is higher. Testing too early or too late may affect the reliability of results. Therefore, an appointment should be made in advance to ensure completion at the appropriate time.
2. Prepare before the examination: Fasting is not required before the test, and normal eating and drinking are allowed. You should bring your prenatal care handbook, identification documents, and other materials. Inform your doctor in advance of the date of your last menstrual period, gestational age, and any previous medical history to help the doctor accurately calculate relevant parameters and provide baseline data for the test.
3. Sample collection: A blood sample is collected from the pregnant woman via venipuncture, typically involving the extraction of 3-5 milliliters of blood. The blood draw process is quick. Afterward, apply pressure to the puncture site with a cotton swab until bleeding stops, avoid rubbing to prevent local bruising, and normal activities can resume after the blood draw without special rest.
4. Testing and risk value calculation: Laboratories test indicators such as maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol. These results, combined with maternal age, gestational age, and weight, are used in specialized software to calculate the risk value of the fetus having Down syndrome. The entire testing process typically takes about 3-7 days.
5. Obtain and interpret the report: After the test, pregnant women should collect the report at the scheduled time. The report will indicate the risk value. A low-risk result suggests a low probability of the fetus having the condition, requiring no further testing. A high-risk result requires further diagnostic tests, such as amniocentesis or non-invasive DNA testing, under a doctor's guidance to confirm the diagnosis.
When undergoing Down syndrome screening, maintain a relaxed mindset and avoid excessive anxiety. After the test, maintain a balanced diet, ensure adequate rest, and follow your doctor's recommendations for regular prenatal checkups to support prenatal health management.
