First-trimester screening is typically performed between which weeks?

First-trimester screening is typically performed between which weeks?

• A. 9-11 Weeks
• B. 10-12 Weeks
• C. 11-13 Weeks
• D. 12-14 Weeks

Answer: (C)

The timing being tested is when screening for aneuploidy in the first trimester is most accurate. The combined first-trimester screen, which uses both an ultrasound assessment of nuchal translucency and maternal serum markers (PAPP-A and free beta-hCG), is performed best in late first trimester. This window—about 11 to 13 weeks of gestation—allows the nuchal translucency to be measured reliably and the serum markers to provide meaningful risk information. If done earlier, NT measurements can be less reliable; if done later, the markers and anatomy may be less predictive for this screen. Therefore, the standard window is 11 to 13 weeks.

The timing being tested is when screening for aneuploidy in the first trimester is most accurate. The combined first-trimester screen, which uses both an ultrasound assessment of nuchal translucency and maternal serum markers (PAPP-A and free beta-hCG), is performed best in late first trimester. This window—about 11 to 13 weeks of gestation—allows the nuchal translucency to be measured reliably and the serum markers to provide meaningful risk information. If done earlier, NT measurements can be less reliable; if done later, the markers and anatomy may be less predictive for this screen. Therefore, the standard window is 11 to 13 weeks.