Measurement of nuchal translucency as a single strategy in trisomy 21 screening: should we use any other marker?
OBJECTIVE
To evaluate the role of nuchal translucency thickness as a single marker in screening for trisomy 21 at 10-16 weeks' gestation.


METHODS
From December 1996 to October 2001, nuchal translucency was measured in 11,281 consecutive early second trimester fetuses referred to our unit for prenatal care and delivery. Scans were performed by eight experienced ultrasonographers, under strict methodological criteria.


RESULTS
Chromosomal abnormalities were found in 118 cases (52 trisomy 21). Using nuchal translucency greater than the 95th centile as a cut-off, the overall detection rate was 71.2% with a specificity of 95.4%, and a positive predictive value of 14%. In the trisomy 21 selected group, detection rate, specificity, and positive predictive value for nuchal translucency were 92.3%, 95.4%, and 8.5%, respectively. The detection rate of trisomy 21 reached 100% when nuchal translucency was measured between 10 and 14 weeks' gestation, maintaining the same specificity.


CONCLUSIONS
Early second trimester nuchal translucency measurement can achieve prenatal detection rates of trisomy 21 greater than 95% with a 5% false-positive rate. With a detection rate so high, the benefits of using additional markers may be less than previously considered. Although maternal age, other sonographic or Doppler markers, and maternal serum biochemistry might play a role in prenatal strategies to detect fetal chromosomal abnormalities, the high detection rate of trisomy 21 fetuses using nuchal translucency as a single parameter suggests that early nuchal translucency measurement between 10 and 14 weeks' gestation can be a simple screening strategy for this condition.
Comas
Carmina
C
Fetal Medicine Unit, Department of Obstetrics and Gynecology, Institut Universitari Dexeus, Barcelona, Spain. carcom@iudexeus.uab.es
Torrents
Margarita
M
Muñoz
Ana
A
Antolín
Eugenia
E
Figueras
Francesc
F
Echevarría
Mónica
M
D000328:Adult; D004314:Down Syndrome / Q000000981:diagnostic imaging / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007621:Karyotyping; D008403:Mass Screening / Q000379:methods; D008423:Maternal Age; D009333:Neck / Q000196:embryology; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal