Evaluation of a fetus for structural or functional cardiovascular disease has become routine now that there is widespread use of fetal ultrasound in obstetrical practice. In addition, greater understanding of the genetic basis for congenital cardiovascular defects has prompted screening of patients who might not have been referred for evaluation in the past. It is important to understand the uses and limitations of fetal echocardiography to optimally utilize this technology and to provide appropriate counseling to parents. This chapter provides a limited overview of fetal cardiology as a foundation for understanding selected aspects of fetal cardiovascular disease. Comprehensive references on fetal cardiology and, in particular, fetal echocardiography are listed at the end of this chapter.
Fetal echocardiography is the primary method for diagnosing fetal cardiovascular disease and monitoring progression and management of the disease process. In centers with experienced fetal echocardiography programs, significant congenital cardiovascular defects can be accurately diagnosed in approximately 95% of cases. Additional information about the application of echocardiography to assess cardiac and vascular function in the fetus is presented in Chapter 3.
A complete fetal echocardiogram is similar in scope to a postnatal transthoracic echocardiogram. Cardiac and great vessel anatomy and relationships, cardiac function, blood flow patterns, and cardiac rhythm are all assessed. A wide range of cardiovascular diseases can be detected and defined in the fetus, including simple and complex cardiovascular structural malformations, cardiomyopathies, tumors, and arrhythmias. Newer techniques of three- and four-dimensional echocardiography are being applied in many centers, but at present, the role of these modalities in improving detection, management, and follow-up requires additional research.
If indicated (see below), the first fetal echocardiogram is generally performed around 18 to 22 weeks’ gestation using a standard transabdominal approach. In some centers, transvaginal fetal echocardiography is offered as early as 11 weeks’ gestation. However, controversy exists regarding the usefulness of early transvaginal ultrasound, and it is not widely used at present. Initial transabdominal studies typically provide excellent resolution of the cardiovascular structures and are sufficiently early in gestation to allow for comprehensive planning.
As discussed in Chapter 15, the incidence of congenital cardiovascular malformations in the United States is around 10 per 1000 live births. The incidence of structural cardiovascular malformations in all pregnancies is not known but it is certainly higher because severe structural or functional cardiovascular malformations may be lethal in the fetus and some mothers elect to terminate the pregnancy if an extracardiac malformation or chromosomal abnormality is detected. In these situations, the presence of a congenital cardiovascular malformation may go unrecognized.
Because a complete diagnostic fetal echocardiogram is time consuming and labor intensive, fetal echocardiography is not well suited for routine screening of all pregnant women. Therefore, it is important to develop a strategy for appropriate targeted referrals for fetal echocardiography. The ...