Cardiac defects, the most common forms of congenital defects, are found in 3-8 of every 1000 pregnancies. Currently only 15-30% of CHD in newborns is detected prenatally. There are different strategies to increase the prenatal detection of cardiac abnormalities. Nuchal translucency screening and ductus venosus blood flow have been suggested to be useful methods of identifying cardiac anomalies in chromosomally normal fetuses.
Objective: To examine the association between nuchal translucency thickness and ductus venosus blood flow between 11-13.6 week of pregnancy and CHD in chromosomally normal fetuses.
Material and methods: Patients with singleton pregnancies at 11 to 13.6 weeks of gestation were recruited to undergo nuchal translucency sonography. The prevalence of major cardiac defects was determined and the utility of screening for nuchal translucency thickness including sensitivity, specificity, and positive and negative predictive values, were calculated for the NT thickness cut off points of the 95th and 99th centile for CRL. Ductus venosus Doppler ultrasound blood flow velocity waveforms were obtained at 10-13.6 weeks gestation.
Results: 4720 gestations were analyzed, of which 13 newborn infants had CHD. The incidence of major CHD increased with increasing NT. Sensitivity specificity and positive predictive values were 45.4%, 92% and 1.5% at 99.8th percentile, and 25%, 98.5%, 3.2% and 99.8% at 99th percentile. Reverse or absent flow during atrial contraction was observed in 8 out of the 13 (61.5%) chromosomally normal fetuses with CHD.
Conclusion: Measurement of fetal nuchal translucency thickness and ductus venosus blood flow at 11-13.6 weeks of pregnancy is a sensitive method of screening for CHD. The prevalence of CHD increases with increasing fetal NT and abnormal ductus venosus blood flow. Increased NT or abnormal ductus venosus blood flow is a strong indication for fetal echocardiography.