Fetal tachycardia is a type of irregular heartbeat known as fetal arrhythmia. Fetal tachycardia occurs when a fetus (developing baby) has a heart rate faster than 180 beats per minute (BPM).

Doctors may diagnose fetal tachycardia if:

  • Fetal heart rate stays above 180 BPM
  • Fetal heart rate goes above 180 BPM at times

Fetal tachycardia is rare. It’s often temporary and harmless. For some, however, fetal tachycardia may require treatment. Fetal tachycardia complications include a dangerous form of fluid buildup called hydrops fetalis.

Fetal Tachycardia Types

There are four types of fetal tachycardia.

Sinus Tachycardia

Sinus tachycardia occurs when a fetal heart rate is above 180 BPM but less than 200 BPM. During sinus tachycardia, the fetal heart is working normally but beating slightly faster than it should.

Supraventricular Tachycardia (SVT)

Supraventricular tachycardia is the most common type of fetal tachycardia. SVT occurs when the heart’s upper chambers (atria) and lower chambers (ventricles) beat faster than 200 BPM.

Atrial Flutter

Atrial flutter occurs when the heart’s top chambers (atria) beat much faster than its lower chambers (ventricles). This condition most often occurs in a structurally normal heart.

Ventricular Tachycardia

Ventricular tachycardia occurs when the heart’s lower chambers (ventricles) beat faster than the upper chambers (atria). Ventricular tachycardia is rare.

Fetal Tachycardia Causes

The causes of fetal tachycardia vary by type.

Sinus tachycardia may be caused by:

  • Excessive thyroid hormone secretion by the mother (maternal hyperthyroidism).
  • Fetal anemia (reduced oxygen in the blood).
  • Fetal distress.
  • Fetal infection.
  • Fever in the mother.
  • Infection in the mother’s uterus.
  • Stimulants (drugs that speed up activities in the body).

SVT is caused by a problem with the heart’s electrical system.

Atrial flutter is caused by a problem with the electrical signal in the heart’s upper chambers (atria).

Ventricular tachycardia is caused by a problem with the electrical signal in the lower chambers of the heart (ventricles). Ventricular tachycardia also has been connected to:

  • Congenital long QT syndrome —a heart signaling problem present at birth
  • Myocarditis—an inflammation of the heart muscle

Fetal Tachycardia Treatment

Some types of fetal tachycardia resolve on their own. Sinus tachycardia, for example, may not require treatment.

Other types of fetal tachycardia may need regular monitoring and treatment. Fetal tachycardia is treated with medications that lower fetal heart rate. These medications are given to pregnant mothers and pass to the fetus through the placenta. Mothers often require admission to the hospital to monitor maternal and fetal response to the medication.

If fetal tachycardia requires medical treatment, doctors will discuss how the diagnosis and treatment may affect a baby’s delivery.

Some babies with fetal tachycardia need care after they are born.

If a baby remains in atrial flutter after birth, doctors use a cardioversion procedure. This restores the heart to its normal rhythm. Cardioversion uses low-energy electric shocks to the outside of the chest. Cardioversion typically cures atrial flutter.

These children may need regular follow-up appointments with a heart rhythm specialist (electrophysiologist) to ensure SVT doesn’t come back.