Specificity of fetal tricuspid regurgitation in prediction of down syndrome in Thai fetuses at 17-23 weeks of gestation

Objective: To assess the specificity of tricuspid regurgitation (TR) in prediction of Down syndrome in Thai fetuses at 17-23 weeks' gestation and to determine the prevalence of TR among normal chromosome fetuses in a high-risk population. Material and Method: A prospective study was performed in 395 high-risk pregnant women who underwent amniocentesis or cordocentesis for fetal karyotyping at 17-23 weeks. The presence or absence of TR was determined by pulsed wave Doppler at the time of prenatal diagnosis. TR was diagnosed when the regurgitation flow was observed for at least half of systole or ≥ 70 milliseconds with maximum velocity of ≥ 100 cm/sec. The diagnostic values of TR for detection of Down syndrome were calculated. Results: The prevalence of TR was 3.8% (14/370) in normal chromosome fetuses and 40% (2/5) in Down syndrome fetuses. Fetuses with TR had a higher chance to be Down syndrome (11.1%) than those without TR (0.8%) (95% CI of the difference, 0.09-32.9, p = 0.036). Specificity, sensitivity, NPV and PPV of TR in prediction of Down syndrome were 95.9%, 40%, 99.2% and 11.1%, respectively. Among normal chromosome fetuses with TR, 14.3% (2/14) had congenital cardiac abnormalities. Conclusion: TR is not only a high specificity secondary ultrasound marker at 17-23 weeks to identify fetuses with Down syndrome in high-risk pregnant women but also associates with the risk of cardiac defects in normal chromosome fetuses.