Prenatal Screening, First-Trimester Screening

Email

Send Email

Recipient(s) will receive an email with a link to 'Prenatal Screening, First-Trimester Screening' and will have access to the topic for 7 days.

Subject: Prenatal Screening, First-Trimester Screening

(Optional message may have a maximum of 1000 characters.)

×


Definition

  • Performed between 11 and 13 weeks of gestation, first-trimester screening combines maternal age plus two serum biochemical markers: pregnancy-associated plasma protein A (PAPP-A) and β-hCG. It also includes fetal nuchal translucency (NT) measurement.

Use

  • Risk assessment for trisomy 21

Interpretation

  • Increased NT associated with trisomy 13, trisomy 18, trisomy 21, 45,X, triploidy, and other chromosome aberrations.

  • Trisomy 21 biochemical profile typically has increased β-hCG and decreased PAPP-A.

  • Trisomy 18 has decreased β-hCG and decreased PAPP-A.

  • Combining NT and maternal serum profile detects approximately 85% of affected trisomy 21 pregnancies with a 5% positive screening rate.

Limitations

  • Does not detect neural tube defects.

  • Detects fewer affected pregnancies than combined first-semester plus second-trimester screening modalities.

  • NT measurement requires experienced ultrasonographers.

 
×