When should NIPT be done?

NIPT is usually offered between 10 and 20 weeks of pregnancy. The lower limit exists for a practical reason: before about 10 weeks there is often too little placental DNA in your blood for the test to work, and you are more likely to get a failed or inconclusive result. The 10 to 20 week window also allows time to follow up a high-risk result with a diagnostic test if you choose to. It is reasonable to have NIPT after 20 weeks if you want the information for reassurance or to help prepare for the birth. Two things NIPT does not replace, and both matter for timing: A first-trimester ultrasound is still valuable. It dates the pregnancy accurately, measures the nuchal translucency, identifies twins, and can pick up structural problems and placental issues. NIPT does none of this. Screening for open neural tube defects, such as spina bifida, is separate. A maternal serum AFP blood test should still be offered at 15 to 20 weeks, because NIPT does not screen for these at all. If you have a high BMI, results are more likely to be inconclusive at earlier gestations, and your doctor may suggest waiting slightly longer.