Objectives To examine the utility of measuring fetal nuchal translucency thickness in screening for major defects of the heart and great arteries at 10-14 weeks of gestation. Design Population based cohort study. Subjects 29 154 singleton pregnancies with chromosomally normal fetuses at 10-14 weeks of gestation. Setting Fetal medicine centre in London. Main outcome measure Prevalence of major defects of the heart and great arteries. Results Of 50 cases with major defects of the heart and great arteries (prevalence 1.7 per 1000 pregnancies) 28 (56%, 95% confidence interval 42% to 70%) were in the subgroup of 1822 pregnancies with fetal nuchal translucency thicknesses above the 95th centile of the normal range. The positive and negative predictive values for this cut off point of nuchal translucency thickness were 1.5% and 99.9% respectively. Conclusions Measurement of fetal nuchal translucency thickness-traditionally used to identify fetuses at high risk of aneuploidy-at 10-14 weeks of gestation can identify a large proportion of fetuses with major defects of the heart and great arteries.

Pathological examination of trisomic fetuses with increased nuchal translucency thickness at 11-13 weeks of gestation demonstrated a high prevalence of cardiac defects and abnormalities of the great arteries. This study reports the pathological findings observed from the examination of the heart and great arteries of 21 chromosomally normal fetuses with increased nuchal translucency. In 19 of the 21 cases there were abnormalities; the commonest was narrowing of the aorta at the level of the isthmus and immediately above the aortic valve. This finding is different from that in case of trisomy 21, where narrowing of the isthmus is associated with an increased diameter of the aortic valve. These findings suggest that abnormalities of the heart and great arteries may be implicated in the pathogenesis of increased nuchal translucency not only in trisomic fetuses but also in chromosomally normal fetuses. It can be implied that increased nuchal translucency thickness at 10-14 weeks of gestation may prove to be a useful marker for the identification of fetal cardiac abnormalities.

Screening for fetal cardiac defects is traditionally based on the ultrasonographic examination of the four-chamber view of the fetal heart at mid-gestation, which has been shown to identify 26% of major cardiac defects. Pathological studies in fetuses with increased nuchal translucency at 10-14 weeks of gestation, a sonographic marker for chromosomal abnormalities, have shown an association between increased nuchal translucency and congenital abnormalities of the heart. This study reports the prevalence of cardiac defects in 1427 chromosomally normal fetuses with increased nuchal translucency thickness, and examines the potential value of this sonographic marker in screening for major cardiac defects. The diagnosis of cardiac defects was made either by postmortem examination in terminations of pregnancy and intrauterine or neonatal deaths or by clinical examination and appropriate investigations in live births. The prevalence of major cardiac defects was 17 per 1000 (24 of 1427 fetuses) and increased with translucency thickness from 5.4 per 1000 for translucency of 2.5-3.4 mm to 233 per 1000 for translucency of > or = 5.5 mm. These findings suggest that measurement of nuchal translucency thickness at 10-14 weeks may prove to be a useful method of screening for abnormalities of the heart and great arteries in addition to its role in screening for chromosomal defects.