Objective: Transvaginal echocardiography is still rarely incorporated into the first-trimester ultrasound examination, despite the fact that heart defects are the most frequently encountered congenital malformation. This study was undertaken to explore the possibilities of fetal echocardiography in the late first trimester.
Methods: In 85 women with uncomplicated singleton pregnancies, three transvaginal ultrasound examinations between 11+0 and 13+6 weeks' gestation were performed. The examinations were carried out at weekly intervals and visualization of several echocardiographic planes was attempted (four-chamber view, aortic root, long axis of the aorta, pulmonary trunk with three-vessel view, cross-over of the great arteries). The diameter of the aorta and pulmonary trunk were measured to establish reference ranges.
Results: The success rate of visualization of the different parameters increased with gestational age. The ability to perform a full cardiac examination increased from 20% in week 11 to 92% in week 13. Longitudinally derived growth curves of the aorta and the pulmonary trunk were constructed and both showed a linear increase with gestational age.
Conclusions: The best time in the first trimester to perform transvaginal echocardiography is at 13+0 to 13+6 weeks' gestation. In this period, a full cardiac examination is possible in 92% of cases. The increase of success rate compared to earlier studies is likely to result from the use of better resolution, high-frequency transvaginal probes. First-trimester echocardiography provides an opportunity to examine the fetal heart early in gestation, especially in patients at risk for cardiac malformations because of a positive family history or in fetuses with increased nuchal translucency.