Fetal arrhythmia: 8 Top things you should know

fetal arrhythmia

During pregnancy, the intricate development of a baby’s cardiovascular system is a marvel to witness. However, there are instances when irregular heart rhythms, known as fetal arrhythmias, can occur. Fetal arrhythmia refers to abnormal heart rhythms in the developing fetus, and while they can be concerning, advancements in medical technology and understanding have made it possible to diagnose and treat these conditions effectively.

Recent studies revealed that fetal arrhythmia, in most cases, is benign. However, the healthcare provider should monitor your baby closely because some types may indicate a heart defect.

Normal fetal heart rate

Fetal heart rate (FHR) refers to the number of times a baby’s heart beats per minute while in utero. This gentle thumping can be detected through various means, including ultrasound, fetal Doppler, or electronic fetal monitoring during prenatal appointments. The fetal heart rate is developing throughout pregnancy. Here is a general overview of the typical fetus heart rate ranges during different trimesters:

  1. First Trimester: During the initial weeks of pregnancy, the fetal heart rate ranges from approximately 100 to 170 beats per minute (bpm).
  2. Second Trimester: The fetal heart rate tends to stabilize as pregnancy progresses. The average range during the second trimester is around 120 to 160 bpm.
  3. Third Trimester: In the final trimester, the fetal heart rate continues to remain within the 110 to 160 bpm range.

To learn more about fetal heart rate range, read our article on Fetal heart rate by week: 7 reasons to monitor baby’s heartbeat.

What is Fetal Arrhythmia?

Fetal arrhythmia is detected in at least 2% of pregnancies during routine check-ups. This medical condition refers to irregular fetal heartbeat. While the majority of pregnancies progress without any complications, the occurrence of arrhythmias highlights the complexity of fetal cardiac development. These irregularities can range from mild and transient to more serious conditions that require medical attention.

Types of Fetal Arrhythmia

Arrhythmia in fetus comes in different forms, each characterized by specific patterns and irregularities. Some of the common types include:

  • Bradycardia. It refers to a slower-than-normal heart rate. While mild bradycardia can be normal, severe cases may require medical attention.
  • Atrial Fibrillation. This condition involves rapid and irregular heartbeats originating in the atria. They are relatively rare in fetuses.
  • Supraventricular Tachycardia (SVT). SVT is characterized by rapid and regular heartbeats originating above the ventricles. While it can be concerning, SVT often resolves without intervention.
  • Premature Atrial Contractions (PACs). PACs are extra heartbeats that occur earlier than expected in the heart’s upper chambers (atria). They are generally harmless and often go unnoticed.
  • Premature Ventricular Contractions (PVCs). Similar to PACs, PVCs involve extra heartbeats, but they originate in the heart’s lower chambers (ventricles). In most cases, PVCs are benign.

Causes of fetal heart arrhythmia

Understanding the causes of fetal arrhythmia is essential for expectant parents and medical professionals alike. Several factors can contribute to the development of these irregular heart rhythms:

Maternal Conditions

Certain maternal health conditions can increase the risk of fetal arrhythmia. Conditions such as diabetes, lupus, or thyroid disorders can impact the baby’s heart development and rhythm.


Some medications taken during pregnancy can affect fetal heart rhythms. It’s important for mothers-to-be to communicate with their healthcare providers about any medications they are taking.

Structural Abnormalities

Issues with the structure of the baby’s heart can lead to irregular heart rhythms. Structural defects can disrupt the normal flow of electrical signals, causing arrhythmia in fetus.

Genetic Factors

In some cases, fetal arrhythmias are associated with genetic mutations or abnormalities. A family history of heart conditions can increase the risk.


Certain infections contracted during pregnancy can affect the developing fetus, including the heart’s development and rhythm.

Electrolyte Imbalance

Imbalances in the levels of electrolytes, such as potassium or calcium, can interfere with the heart’s electrical signaling.

Hormonal Factors

Hormonal changes during pregnancy can influence the heart’s electrical activity, potentially leading to arrhythmias.

Environmental Factors

Exposure to certain environmental factors or toxins can contribute to irregular heart rhythms in the fetus.

Diagnosis and management of heart arrhythmia in fetus

Fetal arrhythmia diagnosis often involves monitoring the baby’s heart rate through methods like fetal heart doppler or echocardiography. Depending on the severity and type of arrhythmia, medical interventions may be necessary. Mild arrhythmias might resolve on their own, while more severe cases could require medications or even fetal procedures. You can detect baby heart skipping beats on doppler while monitoring fetus’s heartbeat at home. In case of detection of irregular heartbeat in fetus, urgently contact your healthcare provider.

Not all fetal arrhythmias require special treatment. If things are stable or improve on their own, no further treatment may be necessary. Heart failures that require treatment depend on the following:

  • causes of heartbeat irregularities
  • mother’s health condition
  • the baby’s health
  • how far along you are in your pregnancy

Word from SonoHealth

In conclusion, the causes of fetal arrhythmia are diverse and multifaceted. While many pregnancies progress without complications, being aware of the potential risk factors can empower expectant parents to seek appropriate medical care and guidance. Through regular prenatal check-ups, open communication with healthcare providers, and a deep understanding of the factors that can contribute to fetal arrhythmia, parents can navigate the journey of pregnancy with confidence and optimism for a healthy outcome.

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