Incidence of major structural cardiac defects associated with increased nuchal translucency but normal karyotype

Objective: To examine the association between increased nuchal translucency thickness and major cardiac defects in chromosomally normal fetuses. Setting: Tertiary referral unit for fetal medicine and fetal cardiology. Methods: During a 4-year period (January 1997 to January 2001), detailed echocardiography was performed in 1319 chromosomally normal fetuses with increased nuchal translucency thickness at 10-14 weeks of gestation. The incidence of major cardiac defects was examined in relation to the fetal NT at the 10-14-week scan. Results: Major cardiac defects were diagnosed in 60 (4.5%) of the 1319 fetuses. In fetuses with a nuchal translucency thickness in the range of 2.5-3.4 mm, the incidence of major cardiac defects was 2.5% (18/722; 95% confidence interval, 1.5-3.9) and in those with a nuchal translucency thickness ≥3.5 mm, it was 7% (42/597; 95% confidence interval, 5.1-9.4). Conclusion: Specialist echocardiography is indicated in all fetuses with increased nuchal translucency thickness because, in such fetuses, the incidence of major cardiac defects is substantially higher than in pregnancies with maternal diabetes, family history and exposure to drugs, where fetal echocardiography is widely considered to be necessary.