What is the optimal time to take the Down syndrome screening test?
I am five months pregnant, and I remember that I need to have the Down syndrome screening (triple test) later. I would like to ask, what is the best time to have this test in terms of gestational weeks?
Doctor's answer (1)
The optimal time for Down syndrome screening can be divided into two stages: early and mid-pregnancy.
The best time for early Down syndrome screening is generally between 9-13 weeks of pregnancy, particularly around 12 weeks, which is considered the most accurate period. This timeframe is chosen because there is less exchange between fetal and maternal blood, and the concentration of fetal cell-free DNA is higher, aiding in more accurate risk assessment.
The optimal time for mid-pregnancy Down syndrome screening is between 15-20 weeks of pregnancy, with 16-18 weeks being ideal. During this stage, there is increased exchange between fetal and maternal blood, resulting in higher concentrations of relevant biomarkers in the mother's blood, making them easier to detect.
Both early and mid-pregnancy screenings can only provide a risk assessment and cannot definitively diagnose Down syndrome. If the screening results indicate a high risk, further diagnostic tests such as amniocentesis or non-invasive prenatal DNA testing are typically required for confirmation.
