First-Trimester Nuchal Translucency Screening for Fetal Aneuploidy

ABSTRACT

The objective was to review current literature pertaining to first-trimester nuchal translucency screening for fetal aneuploidy. To this goal, all manuscripts published in the English language regarding this topic obtained from a MEDLINE search for 1966 through November 1998 were selected and reviewed. Additional sources were identified through cross-referencing. Current widespread application of first-trimester ultrasonography has enabled accumulation of an increasing body of knowledge pertaining to early screening for fetal aneuploidy. Following initial reports, recent studies of large populations of patients (> 500 participants) at either high- or low-risk for fetal chromosomal abnormalities, demonstrate that nuchal thickness of > 3 mm between 10 and 14 weeks' gestation by either transabdominal or transvaginal ultrasonography may serve as screening tool for fetal aneuploidy. Sensitivity and specificity rates improve when first-trimester maternal serum free β-human chorion ic gonadotropin (hCG) and pregnancy associated plasma protein A (PAPP-A) levels are added to this ultrasonographic tool. Current data regarding nuchal translucency including: nomograms, repeatability, optimal timing of measurement, accuracy and effect of confounding factors upon this ultrasonographic measurement, pathophysiology, increased associated incidence of fetal cardiac anomalies, and arrhythmias as well as other structural anomalies, Doppler velocimetry, spontaneous subsequent miscarriage, implications of nuchal translucency in twin gestations, and effect upon performance of subsequent midtrimester maternal serum screening are presented.

Keywords

Prenatal ultrasound - screening - fetal aneuploidy - trisomy 21 - trisomy 18 - first trimester - nuchal translucency