SONOGRAPHIC MEASUREMENT OF NUCHAL SKINFOLD THICKNESS FOR DETECTION OFDOWN-SYNDROME IN THE 2ND-TRIMESTER FETUS - A MULTICENTER PROSPECTIVE-STUDY

Objective: To determine the sensitivity and specificity of soft-tissue nuchal-fold measurement in the second-trimester fetus for the detecti on of trisomy 21. Method: Thirty-six investigators in 12 centers measu red nuchal skinfold thickness in 3308 fetuses of 14-24 weeks' gestatio n. All mothers were referred for amniocentesis because of age, history of genetic disorder, or laboratory findings. Those referred with an u ltrasound indication for amniocentesis, including nuchal-fold thickeni ng, were excluded. Results: Overall, nuchal skinfold was 6 mm or more in 8.5% of chromosomally normal fetuses and in 38% of those with triso my 21. A false-positive rate below 5% was obtained by 81% of the inves tigators. Raising the cutoff of normality to 7 mm after 18 weeks' gest ation improved specificity. Conclusion: Although the diagnostic value of this sign in skilled hands could allow its use as an indication for genetic amniocentesis at the second trimester, the method does not ap pear suitable for population screening because of the high variability in the results among the investigators.