SCREENING FOR DOWNS-SYNDROME BY FETAL NUCHAL TRANSLUCENCY MEASUREMENTIN A HIGH-RISK POPULATION

Objective: To examine the discriminate capacity of nuchal translucency measurement in the detection of trisomy 21 and other chromosomal anom alies. Design: Prospective cohort study. Subjects: A total of 2247 wom en with viable singleton pregnancies between 10 and 14 weeks' gestatio n attending a prenatal diagnosis center for fetal karyotyping. Methods : The fetal nuchal translucency was measured transabdominally in all w omen before invasive prenatal testing. Results: Chromosomal abnormalit ies were found in 63 fetuses, including 36 with Down's syndrome. The l ikelihood of the presence of chromosomal abnormalities increased with larger nuchal translucency thickness. A nuchal translucency of 3 mm or more identified 25 out of 36 fetuses (69%) with trisomy 21 at the exp ense of a 4.0% false-positive rate. Correction of nuchal translucency measurements for differences due to variation of the measurement with gestational age, either by using the 'delta-value' or multiples of the median (MoM), did not improve the detection rate in our patient data set. Conclusions. The discriminative capacity of nuchal translucency m easurement makes it a useful tool in screening for trisomy 21 and othe r chromosomal anomalies.