Fetal Congenital Heart Block


Fetal Cardiology Program at Texas Children’s Fetal Center

832-822-2229 | Referral Fax: 832-824-7333

Congenital heart block, also called atrioventricular (AV) block, is a disruption of the intricate electrical nerve impulse system that regulates the pumping action of the heart. It prevents electrical signals originating in the upper chambers of the heart (the atria) from reaching the lower parts (the ventricles). This interferes with the heart’s normal pumping rate and rhythm.

The disorder may slow or interrupt the heartbeat, making it difficult to pump blood to the rest of the body. Congenital heart block is not a blockage of an artery or blood flow.

Heart block is categorized as first-, second- and third-degree heart block depending on the degree of impairment. First degree is the least severe and third degree is complete heart block.

Symptoms and causes

Congenital heart block is a rare disorder that occurs in about one out of 22,000 live births. It appears equally often in males and females.

Heart block usually develops between 18 and 30 weeks of pregnancy. In most cases, the cause is not known, but babies of mothers with lupus or other autoimmune diseases, or babies with congenital heart disorders, are at higher risk. Also, a tumor on the baby’s heart can cause heart block. These pregnancies should be closely monitored.

Testing and diagnosis

Congenital heart block may be discovered when doctors notice that the upper and lower chambers of the baby’s heart are beating at different rates. A fetal echocardiogram is used to confirm the diagnosis.


Outlook of the condition depends on whether there are additional heart abnormalities, the degree of heart block and the presence of heart failure. Babies with underlying heart disease, a very slow heart rate (<55 beats/minute), or with hydrops, often face a poor outcome.

Those with complete heart block may need a pacemaker at a very young age and will need to be cared for by an electrophysiologist, a doctor who specializes in electrical problems of the heart.

After birth, children with milder forms of congenital heart block will need to be monitored by a pediatric cardiologist regularly.


All forms of congenital heart block are managed by a multidisciplinary team that may include a fetal cardiologist, maternal fetal medicine specialist, a pediatric electrophysiologist (rhythm specialist) and adult cardiologist. When you choose Texas Children’s for your child’s care, you choose the #1 pediatric heart center in the country. The Fetal Heart Program can monitor both baby and mother throughout the pregnancy and create a plan for labor and care after the birth.

The recommended treatment for your baby will depend on the type of heart problem present and its severity. However, the earlier a problem is identified, the better you and your physicians can prepare to give your baby the best outcome possible.

In some cases, it may help a baby with congenital heart block for the mother to receive steroids during her pregnancy. This may help improve electrical impulse conduction in the baby’s heart.

After birth, your baby may need a pacemaker implanted and followed life-long by an electrophysiologist.

Support and preparation for the family also is an important focus for the team. With this in mind, our Fetal Cardiology Program works in conjunction with many other teams at Texas Children’s Hospital to provide the most complete fetal diagnosis and monitoring.

See an example of what fetal complete congenital heart block looks like on a fetal echocardiography.

Volumes and outcomes

For more information or to schedule an appointment, call Texas Children’s Fetal Center at 832-822-2229 or 1-877-FetalRx (338-2579) toll-free.

Our phones are answered 24/7. Immediate appointments are often available.