Evaluation of first-trimester screening by fetal nuchal translucency and maternal age.

The aim of this screening study was to evaluate first-trimester screening for chromosomal defects by fetal nuchal translucency thickness at 10-14 weeks of gestation in four Fetal Medicine Units in Greece. Estimates of the risk for trisomy 21 were calculated taking into account fetal nuchal translucency thickness and maternal age. There were 3550 cases; the median maternal age was 29 years (range 16-48 years); and 277 (7.8 per cent) were over 37 years. The median crown rump length was 60 mm (range 38-85 mm) and the fetal nuchal translucency thickness increased with crown rump length and measurements were above the 95th centile in 101 (2.9 per cent) of the cases. The adjusted risk was 1 in 300 or more in 172 (4.9 per cent) of the cases and the high-risk group contained ten of the 11 (91 per cent) fetuses with trisomy 21 and all 11 fetuses with other chromosomal defects. The findings of this study provide further evidence for the high efficacy of screening for chromosomal abnormalities by fetal nuchal translucency and maternal age.