ABC | Volume 112, Nº5, May 2019

Guideline Brazilian Fetal Cardiology Guidelines – 2019 Arq Bras Cardiol. 2019; 112(5):600-648 with trisomy. When present in chromosomally normal fetuses, the risk of heart disease is observed to increase eight-fold. The etiology of tricuspid regurgitation in the first semester is uncertain; it is known only that it disappears concomitantly with the normalization of nuchal thickness. 24 2.4. Fetal Echocardiography Before beginning the examination, it is very important to obtain information regarding gestational age, previous obstetric history, possible maternal disease or use of medications that may increase the risk for CHD, and the formal indication for the study. This will provide the cardiologist with the possible risks for cardiac anomalies. The ultrasound system may be specific for echocardiography or ultrasonography, provided with a preset for fetal heart/echocardiography. Convex (ultrasonography) or phased array (echocardiography) transducers allow to obtain good quality images, with the observation that the majority of convex transducers do not provide continuous Doppler, which may be useful in cases of valvular stenosis or regurgitation. Volumetric transducers may allow better two- dimensional imaging in obese pregnant women and first trimester examination, but they are not essential in daily practice, being considered sophisticated technology not available in the majority of fetal scanning laboratories. After 18 weeks gestation, all cardiac structures may be securely analyzed by the fetal echocardiogram except in cases of poor acoustic windows like obesity, polyhydramnios, oligohydramnios and others. The best images, however, are obtained between weeks 24 and 28, when the heart is larger in size, the fetus continues moving well, and the bones do not constitute a significant ultrasound barrier. It is worth highlighting that early evaluation of the heart may be performed either by transvaginal or transabdominal ultrasound (after week 14); this is usually indicated in pregnancies with high risks of fetal heart disease, especially when screening at the first trimester is indicative of cardiac anomaly. 24 It is essential that the fetal cardiologist has a basic understanding of ultrasonography concepts, particularly regarding fetal status and position. Before beginning the evaluation of the heart, the position of the fetus must be determined, identifying right and left sides. The main marker of the fetal left side is the stomach. In the event of situs inversus or situs ambiguous, the stomach may be displaced, and should not be used as a marker of the fetal left side. The best image of the heart is obtained from the abdomen, sliding the transducer slightly toward the thorax. Although it is also possible to obtain images from the front or the back of the baby, the images obtained from the back may be of inferior quality, especially during the last trimester, when the ossification of the ribs and the spine represents an important barrier to ultrasound passage. In this situation, to improve image quality, one may request patient to lie in left or right lateral decubitus position. Polyhydramnios is a condition that may pose great difficulties to perform the examination, since the fetus may be too far from the transducer and move constantly. Perform measurements and place the Doppler sample volume in place to obtain the usual traces may be really challenging. In situation like this, the fetus may be brought closer to the transducer, if the patient lies or her knees and elbows. Maternal obesity also poses difficulties to the technical quality of the study and it is often needed a low-frequency transducer, sometimes such as those used for adult echocardiography with more vigorous compression to the maternal abdomen. Once the fetal heart has been identified, only small movements of the transducer are necessary to analyze all the cardiac structures. Considering that the fetal heart is relatively far from the transducer, small movements mean big changes in angle. Fetal echocardiography is considered complete when the heart has been examined from all possible views and planes, including the projections obtained in a conventional postnatal echocardiogram. Differently from the recommendations for obstetric screening for cardiac malformations, fetal echocardiography must include transverse and longitudinal views of the fetus, what guarantees different sights of the same structure. 18 The following images should also be included to the 6 transverse levels: long axis of the aortic and ductal arches (Figures 2.3 and 2.4), bicaval view (Figure 2.5), and short axis of ventricles and great vessels (Figures 2.6 and 2.7). 2.5. Imaging Techniques Used on Fetal Echocardiography Experienced imaging professionals, such as ultrasound specialists, radiologists, or echocardiographers may evaluate the fetal heart with high diagnostic accuracy. However, knowledge of the anatomical, physiological and possible therapeutic algorithms are essential to obtain the most accurate information and counsel the family. To avoid missing information, the international medical societies of echocardiography and ultrasound have established the obligatory contents of a complete fetal echocardiogram. Based on the AHA guidelines published in 2014, mandatory elements (Class of Recommendation I), elements whose inclusion is reasonable (Class of 608