In order to understand a fetal echocardiogram, it’s critical to start with what it’s used to detect. In the United States, congenital heart disease (CHD) is the most common type of birth defect, impacting nearly 1 percent of (or about 40,000) births every year.
The most common type of CHD is a ventricular septal defect (VSD). Close to 25 percent of infants with CHD have a critical defect, and these infants typically require surgery or some other kind of intervention in their first year of life.
A fetal echocardiogram is an ultrasound test performed during pregnancy to evaluate the fetal heart.
A small probe called a transducer is placed on the mother’s abdomen, which emits sound waves at a frequency too high to be heard. The ultrasonic sound waves move through the mother’s and baby’s skin, to other body tissues and finally to the baby’s heart, where the sound waves bounce off the heart structures and return to the transducer. The transducer detects the reflected waves and sends them to a machine for interpretation, resulting in a generated image of the heart. This test isn’t painful and causes no harm to the baby. On average, it takes about 45-90 minutes to perform, depending on the complexity of the fetus’ heart.
Unlike an ultrasound (anatomy scan) performed routinely at an obstetrician’s office to examine every fetal structure, a fetal echocardiogram is a focused evaluation of the fetal heart. It allows a pediatric cardiologist to assess the cardiac structure and function in detail. This test is performed by an ultrasound technician, also known as a “sonographer,” and is interpreted by a pediatric cardiologist who has a specialization in fetal cardiac imaging.
Fetal echocardiography can detect heart abnormalities before birth, allowing appropriate pre-delivery planning and medical management once the baby is born. This is important for babies with severe heart defects to ensure a well-coordinated birth plan for the mother and baby. Some infants with severe heart defects will require special medications, surgeries or procedures soon after birth.
Who should receive a fetal echocardiogram?
A fetal echocardiogram isn’t necessary for every pregnant woman. The prenatal ultrasound tests performed routinely by an obstetrician can provide information regarding whether the fetal heart has properly formed. Most fetuses do not require a fetal echocardiogram.
The following are the most common indications for a fetal echocardiogram:
- A routine prenatal ultrasound has discovered a possible structural heart defect
- A routine prenatal ultrasound has discovered a possible arrhythmia in the baby
- Family history of a sibling or parent born with a CHD
- A chromosomal or genetic abnormality is discovered in the baby (such as, but not limited to, Trisomy 13, 18 or 21, also known as Down’s syndrome)
- Extra fluid found around the fetal organs (heart, skin, liver and lungs)
- If abnormalities of multiple organs, such as the kidney, bones or brain, are detected
- Certain types of twin pregnancies
- Lung abnormalities, such as congenital diaphragmatic hernia, a lung malformation or a lung tumor
- If the mother has taken certain medications that may cause CHDs, such as certain anti-seizure, anti-depressant, antibiotic, anti-inflammatory (i.e. ibuprofen, indomethacin) or prescription acne medications
- If the mother abused alcohol or drugs during pregnancy
- If the mother has diabetes, lupus, Sjögren’s syndrome, phenylketonuria or a connective tissue disease
- If the mother had rubella during pregnancy
When is a fetal echocardiogram performed?
Fetal echocardiograms are typically performed in the second trimester of pregnancy, most commonly between 18-24 weeks gestation. In rare circumstances, pediatric cardiologists can obtain images of the fetal heart as early as 11-13 weeks gestation. However, should a scan be performed this early, the mother will likely be asked to return for more definitive images later in gestation to confirm the earlier findings.
If an obstetrician detects a structural heart abnormality, the mother will be referred to a pediatric cardiologist for a more detailed diagnosis and counseling. Following a fetal echocardiogram, the pediatric cardiologist will review the findings with the family in detail and determine whether further follow-up during pregnancy or following delivery is necessary. Depending on the severity of the heart defect, the mother might see a fetal cardiologist once or even multiple times during her pregnancy. If the fetal echocardiogram is normal, the mother will usually be discharged from the cardiologist or, in some cases, the infant will undergo an echocardiogram after birth.
When a heart defect is detected, the pediatric cardiologist will explain the diagnosis and implications in detail as soon as the study is completed. In many cases, the cardiologist may take additional images after the sonographer has completed the initial study. The pediatric cardiologist will often draw pictures to explain the significance of the heart defect, including whether or not the defect will impact the fetus prior to birth, require immediate transfer after birth (to the neonatal or cardiac intensive care unit) and/or require heart surgery after birth. Follow-up visits might include meeting additional specialists, such as a fetal care coordinator, genetic counselor, cardiac surgeon or interventional cardiologist to ensure the child delivers at the correct facility and to learn more about heart surgery or other procedures that may be required after birth.
It’s important to note that even in the case of a normal fetal echocardiogram, the test has inherent limitations, as the blood circulation in the fetus is different than it is after birth. Some limitations include the inability to rule out small holes (such as atrial or ventricular septal defects), a pulmonary venous abnormality (also known as partial anomalous pulmonary venous return), minor valve abnormalities (including bicuspid aortic valve), and coarctation of the aorta. Despite these limitations, a normal fetal echocardiogram is largely reassuring of a very low likelihood of structural heart disease.
For any pregnancy involving a complex heart disease, it’s recommended to deliver in a large hospital setting with access to health care specialists and services to support the baby following delivery, such as a neonatal intensive care unit (NICU) and cardiovascular intensive care unit (CVICU). Texas Children’s Hospital and Texas Children’s Pavilion for Women are nationally recognized centers for the care of fetuses and infants with CHDs.
If you're interested in learning more about the Fetal Cardiology Program at Texas Children's Fetal Center, click here.