Nuchal translucency as a screening test for chromosomal abnormalities in a routine first trimester ultrasound examination.

Background: To evaluate the implementation of nuchal translucency measurement as an additional examination within the first trimester routine ultrasound in an unselected population of women.

Methods: A prospective study in which all pregnant women during 1994, referred for the first trimester routine ultrasound scan, were asked to participate. Of a total of 1852 women with a viable pregnancy, results from 1444 women were evaluated. When a nuchal translucency of 4 mm or more was found, the woman was offered both a genetic amniocentesis in gestational week 13-15 and an additional ultrasound examination in gestational week 18-19.

Results: Six fetuses had a nuchal translucency of 4 mm or more and none of these had any chromosomal abnormality. Neither had any of the fetuses in the study, karyotyped for other reasons, any chromosomal defect and nor was there any child born with aneuploidy in the study population. No strong relation between major malformations e.g. abnormalities of the heart and increased nuchal translucency was found. The fetus with the largest nuchal translucency (=6 mm) was born healthy.

Conclusion: The efficacy of nuchal translucency measurement needs further evaluation before it can be introduced as a screening method in an unselected pregnant population.