Diagnosis, causes, treatment and more

A healthy fetal heart rate is between 110 and 160 beats per minute. A faster or slower heart rate may indicate there is a problem that needs further attention.

An arrhythmia, or irregular heartbeat, occurs when the heart beats too fast, too slow, or with an irregular rhythm.

Fetal arrhythmia is an abnormal fetal heartbeat or rhythm. According to an article in the Indian Pacing and Electrophysiology Journalthe normal fetal heart rate is between 110 and 160 Beats per minute (bpm).

Doctors diagnose fetal arrhythmias in 1-3% of pregnancies. While most fetal arrhythmias are benign, certain cases may require medical intervention.

This article explains how doctors diagnose fetal arrhythmia, the different types, possible causes, and treatments.

Doctors can detect fetal arrhythmias with ultrasound. If a doctor suspects an arrhythmia after reviewing a person’s routine ultrasound, they may recommend a fetal echocardiogram.

A fetal echocardiogram (fECG) is a safe and non-invasive test that allows a pediatric cardiologist to see the structures of the heart. The test can take place anywhere between 45 and 120 minutesdepending on the complexity of the heart of the fetus.

Fetal magnetocardiography (fMCG) is not yet widely available. However, it can provide a more accurate picture of a fetus’s heart than the fECG. Doctors can use fMCG to diagnose abnormal heart rhythms in fetuses 20 weeks gestation and older.

A doctor may also order other tests, such as:

Learn more about arrhythmias here.

Sometimes doctors can’t tell what’s causing an arrhythmia. There is however common causesincluding:

  • Problems with the heart’s electrical signals
  • structural abnormalities in the heart
  • congenital heart defects
  • restricted blood flow to the heart or ischemia
  • electrolyte imbalances

There is many Types of fetal arrhythmias. They include:

Extrasystoles or Preterm Labor (PCs)

That most common Type of fetal arrhythmia is preterm labor or PCs. This arrhythmia occurs when the fetus has extra heartbeats or ectopic beats that originate in the atria (PACs) or the ventricles (PVCs). PVCs are less common than PACs.

While most PACs are harmless and usually disappear over time, roughly 1% of fetuses with PACs have significant structural heart disease. Another 0.5% develop supraventricular tachycardia.

Fetal PVCs also usually resolve over time. However, doctors will monitor them closely can lead to Proxysmal ventricular tachycardias (VTs).

tachyarrhythmias

Fetal tachycardia refers to a faster heart rate than 180 bpm. It could happen if a pregnant person:

Fetal supraventricular tachycardia (SVT) is the most common form of fetal tachycardia. It occurs when the fetus’s heart rate is faster than 220 bpm. SVT complicated about 1 in 1,000 pregnancies and can lead to hydrops or heart failure.

Doctors can diagnose sinus tachycardia (ST) when the fetal heart rate is between 180 and 200 bpm.

Atrial tachycardia (AT) occurs when the heart’s upper chambers, the atria, beat too fast. Ventricular tachycardia (VT) occurs when the heart’s lower chambers, the ventricles, beat too fast and can’t pump enough blood around the body. AT is more often as VT.

bradyarrhythmias

Doctors can diagnose fetal bradycardia when the fetus’s heart rate is too slow 110 bpm for 10 minutes or more. Persistent fetal bradycardia is relatively uncommon and can result from:

  • congenital anomalies
  • Damage to the sinus node (SA).
  • Ion channel dysfunction, such as long QT syndrome
  • Inflammation and fibrosis of the SA node
  • viral myocarditis
  • collagen vascular diseases
  • Medications taken by the pregnant person, including beta-blockers and sedatives
  • rare metabolic diseases such as Pompes disease

About 30% of cases of sustained bradycardia resolve without treatment.

Types of fetal bradycardia include:

  • sinus bradycardia
  • blocked atrial ectopic beats
  • atrioventricular (AV) heart block

Every case of fetal arrhythmia is different, and not all fetal arrhythmias require treatment. Many will resolve themselves.

Doctors prescribe treatment based on the cause of the fetal arrhythmia, the health status of a pregnant person, the health status of the fetus, and the stage of pregnancy.

Medications are the most common way to treat a fetal arrhythmia. When a pregnant person takes medication, it passes through the placenta to the unborn child. A pregnant person can take medication this contains:

After birth, doctors carefully monitor the baby’s heart rate and may recommend additional medications.

Fetal arrhythmias are relative common and account for 10-20% of referrals to fetal cardiology. The outlook for fetal arrhythmia depends greatly on the type and severity of the condition.

PCs is the most common type of fetal arrhythmia. It has a good prognosis and does not affect the growth and development of the fetus.

When doctors can accurately diagnose fetal arrhythmias, they can choose the best pre and postnatal treatments for a baby.

Persistent fetal arrhythmias can lead to Hydrops, cardiac dysfunction, or fetal death.

To learn more about fetal arrhythmia and heart disease affecting children, including finding support groups, a person can consult a family doctor or cardiologist for referrals. Alternatively you can visit:

Most fetal arrhythmias are benign and go away on their own. Doctors typically use a fetal echocardiogram to diagnose fetal arrhythmias. However, you can use other tests as well.

Doctors prescribe medications to treat fetal arrhythmias. They consider several factors before selecting treatments, including the mother’s health and the severity of the condition.

Untreated fetal arrhythmias can result in hydrops, cardiac dysfunction, or death in the fetus.

Doctors monitor the health of the fetus and the pregnant person throughout pregnancy and after birth. A baby may need further treatment if the arrhythmia doesn’t go away on its own.

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