How many weeks pregnant for the NIPT blood test?

What does the evidence say about NIPT test timing during pregnancy?

1. Clinical reviews describe 10 weeks as the usual lower boundary for NIPT because placental cell-free DNA fraction is lower earlier in pregnancy. 1
2. Fetal fraction tends to rise with gestational age, while maternal weight and other factors can affect whether a sample produces a reportable result. 2
3. A systematic review describes fetal fraction as commonly around 10% to 15% between 10 and 20 weeks, with variation among patients and methods. 3
4. A prenatal screening guideline recommends cell-free DNA screening after 10 weeks and explains that screening is distinct from follow-up testing. 4
5. A low fetal fraction or no-call result should be discussed with the prenatal team because redraw timing, another screening method, or follow-up testing depends on the reason and gestational timing. 2

Is NIPT test timing safe in each trimester?

• First trimester. NIPT is generally discussed from about 10 weeks. Your clinician can review dating, fetal fraction factors, and whether another screening or follow-up option fits.
• Second trimester. If testing is done in the second trimester, your clinician can explain how NIPT fits with other screening and what a high-risk or no-call result means.
• Third trimester. A late test may still be possible, but timing depends on your care plan and the decision window for follow-up. Ask what result and follow-up options remain available.