First trimester fetal echocardiography: where are we now?

The detailed study of the fetal cardiac anatomy in the first trimester of pregnancy by means of ultrasound is feasible whether using a transvaginal or a transabdominal approach. There is nowadays enough evidence that ultrasound in the first trimester of pregnancy is a safe procedure provided thermal and mechanical indices are taken into account. The best timing for successful imaging of the four chambers and great arteries in early gestation appears to be between around 13 to 14 weeks rather than 11 to 12 weeks. In experienced hands, first-trimester fetal echocardiography is quite sensitive for the detection of major structural cardiac abnormalities. Besides the nasal bone, markers for first trimester screening of chromosomal abnormalities such as nuchal translucency thickness, the flow in the ductus venosus and the flow through the tricuspid valve constitute also markers for cardiac abnormalities. The finding of an increased nuchal translucency, an abnormal flow in the ductus venosus or a tricuspid regurgitation constitutes an indication for more detailed fetal cardiac assessment. Other indication for a detailed cardiac assessment is the finding of an aberrant right subclavian artery and vascular anomalies. The emerging importance of these markers has caused renewed interest in the early study of the fetal heart.