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What is Fetal Arrhythmia?

Arrhythmia and dysrhythmia, which describe abnormal and irregular heartbeats, can happen to babies still in the womb. Some types of irregular and abnormal heartbeats are relatively benign and will not affect your baby at all; others types can cause mild or serious complications.

There are many types of arrhythmia and dysrhythmia, and they vary in severity:

  • Tachycardia
    • The heartbeat is too fast
  • Supraventricular Tachycardia
    • A rapid heart rhythm that begins in the upper chambers of the heart.
  • Ventricular Tachycardia
    • A rapid heart rhythm that starts in the bottom chamber of the heart. This is less common in a fetus. Bradycardia The heartbeat is too slow.
  • Complete Heart Block
    • The heartbeat that starts in the atrium does not connect to the ventricle. A person with complete heart block may require a pacemaker. Benign Irregular Heartbeats The heart beats at irregular intervals, but these irregular beats do not have any long-lasting effect, and are most commonly premature atrial contractions.
  • Premature Atrial Contractions
    • The heartbeat originates in a different part of the atrium than it normally would. These often occur in healthy people, have no symptoms, and do not cause problems. In rare cases they can initiate tachy or brady arrhythmias that need intervention or monitoring.

How common is Fetal Arrhythmia?

Fetal tachycardia, which is the most common of these arrhythmias, occurs in about 1 out of 200 pregnancies. Many of these are fairly common and can be well-controlled with medication.

How is Fetal Arrhythmia diagnosed during pregnancy?

If your doctor suspects an arrhythmia after reviewing your routine ultrasound, he or she may request a fetal echocardiogram (ECHO), or an ultrasound of the fetus’ heart. The ECHO shows the structure of the heart and evaluates the contractions in different chambers of the heart, which can help us confirm the diagnosis and decide on the best option for treatment.

How is Fetal Arrhythmia monitored and treated during pregnancy?

Premature beats have very little, if any, effect on a fetus. Fetal tachycardia or bradycardia however, can cause heart failure either in the womb or at birth.

Bradycardia, if related to complete heart block needs to be closely followed in-utero to watch for development of heart failure. Mothers with autoimmune disease, and specific antibodies can be at risk for this. The antibodies can cross the placenta and damage the conduction system of the baby’s heart.

Supraventricular tachycardia may require treatment before birth, because it can result in heart failure. Typically, mothers are hospitalized and started on medicines that can cross to the baby and help control the heart rate. After delivery, these babies are generally monitored and on medication for six months. Many tolerate coming off the medicine without recurrence. For mothers who are on medication for their baby’s heart, our team at the Fetal Care Institute will monitor your baby closely during the pregnancy, and help coordinate a delivery plan.

How does Fetal Arrhythmia affect delivery, and how is it treated after birth?

Most babies with arrhythmia can be delivered normally at full-term. With some more severe forms of arrhythmia, though, your baby may need to be delivered early or via C-section. At the Fetal Care Institute, we monitor your baby closely during delivery to minimize complications and make state-of-the-art care available immediately. In most cases, after delivery, your baby will be given medication and treated in the neonatal intensive care unit (NICU). With more severe arrhythmias, such as severe bradycardia and complete heart block, your baby may need a pacemaker implanted.

What happens after the surgeries, and what is the long-term prognosis?

Overall, if treated early, the long-term prognosis for most arrhythmias is quite good—most of these cases have excellent outcomes. Most babies with tachyarrhythmia will need to be on medication for the first six months of their lives to regulate their heartbeats. After that, they will need regular follow-up visits with a cardiologist to monitor their progress, but will likely lead normal and healthy lives. In the case of bradycardia that require surgery or a pacemaker, the prognosis is still very good—most treatments are successful, and in most cases, these children lead normal and healthy lives as well.