Protocols for High-Risk Pregnancies

Table 6.1 Indications for fetal echocardiography

Full fetal echocardiography includes obtaining all the views in the fetus routinely obtained in postnatal echocardiography ( Table 6.2) using both real‐time gray‐scale and color Doppler imaging. Additionally, spectral Doppler, cardiac biometry, and M‐mode data can be obtained as indicated. Fetal echocardiographers use these latter techniques variably. The two‐dimensional examination should be sufficient to exclude significant heart disease in the vast majority of affected individuals. The more sophisticated studies are especially useful in cases of suspected structural or functional abnormalities.

In a recent Practice Parameter, the AIUM has described required and optional components of the detailed fetal echocardiographic examination, shown in Table 6.3.

Table 6.2 Standard fetal echocardiographic views and what to see

Table 6.3 AIUM recommended components of detailed fetal echocardiographic exam

When a cardiac anomaly is found, a full detailed fetal scan to detect any other extracardiac anomalies is mandatory. Many fetal syndromes include cardiac anomalies, and accurate counseling requires complete enumeration of associated anomalies. Fetal karyotype testing should be offered to the parents, as chromosome abnormalities are seen in a large segment of fetuses with congenital heart disease. Additional testing for a microdeletion of chromosome 22q11 can be helpful in fetuses with conotruncal malformations (e.g., tetralogy of Fallot, truncus arteriosus). As for all fetal anomalies, microarray testing for microdeletions and microduplications has also become routine. In selected cases specific gene sequencing or even whole exome or genome sequencing is indicated.

Overall survival once a cardiac lesion is found depends on the nature of the cardiac problem, the presence of extracardiac anomalies, the karyotype, and the presence of fetal hydrops. Fetal hydrops in association with structural heart disease is virtually universally fatal. Aneuploid fetuses may have dismal prognoses even in the absence of heart disease; for example, fetal trisomy 18 may make repairing even a straightforward ventricular septal defect inadvisable.

Lesions that can be repaired into a biventricular heart carry a better long‐term prognosis than those that result in a univentricular heart. In general, infants known to have congenital heart disease prenatally do better than those whose cardiac defects are only found after birth.

The largest group of fetal arrhythmias are intermittent and due to atrial, junctional or ventricular extrasystoles. They carry a small risk of co‐existent structural abnormality. A greater risk exists of an unrecognized tachyarrhythmia, or the development of a tachyarrhythmia later in gestation. Atrial extrasystoles predispose the fetus to development of reentrant atrial tachycardia, which can lead to fetal hydrops. We recommend weekly auscultation of the fetal heart, along with avoidance of caffeine or other sympathomimetics, until resolution of the arrhythmia.