2 The Fetal Echocardiogram
Background
A variety of maternal or fetal disorders may place a fetus at increased risk for congenital heart disease (CHD) (Table 2-1). If present, a fetal echocardiogram is indicated, and timely referral is recommended. Combined, approximately 5% of pregnancies are referred for in utero evaluation. Abnormal or unsatisfactory (the inability to establish normal) cardiac views obtained as part of an obstetric anatomic survey account for more than 20% of all referrals for in utero evaluation and lead to more than half of all prenatal diagnoses. The anatomic survey, a nearly universal mid-pregnancy ultrasound scan, includes a four-chamber (4C) view of the heart and, if possible, views of both outflow tracts. A positive family history accounts for another nearly 20% of all referrals. However, these are the source of less than 5% of all prenatal diagnoses.
TABLE 2-1 INDICATIONS FOR FETAL ECHOCARDIOGRAPHY
| Maternal Indications | Fetal Indications |
|---|---|
| Family history of CHD including prior child or pregnancy with CHD | Abnormal obstetric screening ultrasound |
| Metabolic disorders (e.g., diabetes) | Extracardiac abnormality |
| Exposure to teratogens | Chromosomal abnormality |
| Exposure to prostaglandin synthetase inhibitors (ibuprofen) | Arrhythmia |
| Infection (rubella, coxsackie virus, parvovirus B19) | Hydrops |
| Autoimmune dx (e.g., Sjögren syndrome, SLE) | Increased first trimester nuchal translucency |
| Familial inherited disorder (Marfan, Noonan syndromes) | Multiple gestation and suspicion for twin-twin transfusion syndrome |
| In vitro fertilization |
Cardiac Embryology and In Utero Physiology
Cardiac Embryology
Overview
A complete fetal echocardiogram includes two-dimensional (2D) evaluation of cardiac anatomy, spectral and color Doppler interrogation, and an assessment of cardiac function and rhythm. The components of a comprehensive evaluation are listed in Table 2-2, although not all may be visualized in every fetus at every examination. Similar to transthoracic imaging, fetal echocardiography depends on the ability to obtain standard views and evaluate structures in orthogonal views. The fetus may be very active, and the examiner may need to piece together many partial images to form a composite picture, particularly in the presence of complex CHD.
TABLE 2-2 COMPONENTS OF THE FETAL ECHOCARDIOGRAM
| Overview | |
| Biometric examination | |
| Cardiac imaging | |
| Doppler examination | |
| Measurement data | |
| Examination of rate and rhythm |
