Chapter 4

Evaluation of a fetus for structural or functional heart disease is commonplace, as the application of clinical fetal ultrasound has become widespread in modern obstetrical practice. Furthermore, our current understanding of the genetic basis for congenital heart defects prompts screening in patients who otherwise 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. The purpose of this chapter is to provide a brief overview of fetal cardiology that can be used as a foundation for understanding selected aspects of fetal heart disease. More 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. This chapter will provide a succinct overview of fetal echocardiography to provide basic information about its indications and limitations, and will discuss how to apply findings from a fetal echocardiogram to the patient. 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 subsequent discussion), the first fetal echocardiogram is generally performed around 18- to 20 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. Transabdominal studies performed at around 18 to 20 weeks gestation provide excellent resolution of the cardiovascular structures and are sufficiently early in gestation so that elective termination can be considered if the family so desires.

### Indications

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 precisely, but it is most certainly higher for at least three reasons: (1) severe structural or functional cardiovascular malformations may not permit survival of the fetus; (2) some mothers elect to terminate the pregnancy if an extracardiac malformation or chromosomal abnormality is detected; and (3) the structural defect may be subtle or even nonexistent in the fetus, and may manifest only after birth when the circulation transitions to ...

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