First Trimester Screen
First trimester screening of risk for trisomy 21 and trisomy 18 involves measuring serum levels of pregnancy-associated plasma protein A (PAPP-A) and human chorionic gonadotropin (hCG), combined with maternal age risk and a fetal nuchal translucency (NT) measurement.
Sonographers should be certified through the Nuchal Translucency Quality Review (NTQR) program or the Fetal Medicine Foundation (FMF). Specimens are accepted when the crown-rump length (CRL) measures 45.0 – 84.0 mm.
- Gestational age: 11 – 13 weeks 6 days
- Nuchal translucency ultrasound required