This leaflet is to help you understand what an Irregular or Abnormal Heart Beats is, why it happens, and the implication of being diagnosed for you and your baby.

What does irregular beats mean?

The fetus heart should beat in a regular rhythm. This means that fetal heart rate exhibits a sustained regular rate in the order of 120-160 beats per minute in the second and third trimesters. Sometimes an additional beat or missed beat is noticed during the assessment of the fetal heart in your antenatal visits or when you are examined by ultrasound. According to where the irregular beat originates in the heart chambers those beats are either called premature atrial contractions or premature ventricular contractions.

Premature atrial contractions are by far more common and in fact, they are the most common problem when it comes to problems of the fetal heart rhythm. Most adults also experience these missed or extra beats in their own heart rather frequently.

Why does irregular beats occur?

Your fetal heart pumps because it is under the control of an electrical system. This electrical system is in turn under the control of a particular place in the heart called the sino-atrial node which is located in the right atrium. Irregular beats occur when electricity starts anywhere else. Because the electricity starts before its time, the heart will either beat before its time (extra beat) or the electrical system will stop this abnormal beat (missed beat). In both cases, a pause (very transient stop) will be present in the heart.

How frequent are irregular fetal heart beats during pregnancy? 

They are very frequent. No less than 1% of pregnancies exhibit these extra, irregular beats.  They are one of the very common reasons why patients are sent to the fetal cardiology service for assessment. 

Why are they frequent during pregnancy?

It is said that because the electrical system in the fetal heart is immature, those irregular beats are common. With increasing gestation, the electrical system of the fetal heart matures and those irregular beats go away.

Do irregular beats tell that the fetal heart is abnormal?

The vast majority of these extra beats occur in completely normal hearts. Their presence does not mandate a structural problem in the fetal heart. However, your fetus should be examined for structural heart problems. 

My doctor asked me to come back because of irregular beats; do I need to worry?

The vast majority of these abnormal, irregular beats are very benign and go away on their own, very frequently before birth, or shortly after you deliver your baby. However, your doctor will ask you to come back until s/he makes sure that the irregular beats have resolved, especially if they are frequent. In a minority of cases, a more serious rhythm abnormality may develop, and your physician will make sure this does not happen. Fortunately, this is not common.

Is there any specific treatment for irregular beats?

No. Most of those beats go on their own without any medication whatsoever. You will just be asked to come back to make sure that those irregular beats are no longer present and that the more serious rhythm problems which occur in a minority of cases did not happen.

Should I have more tests done? 

Most of the ectopic beats are diagnosed in the second trimester, when you should have done your second trimester anatomy scan which includes assessment of the fetal heart. If you did not perform this scan at the time of diagnosis of irregular beats, your doctor will ask you to perform it. Other than that, no more tests are needed. 

What are the things to watch for during pregnancy?

Ectopic beats most of the time go away on their own. You will only be asked for follow-up until they are no longer present. Aside from this follow-up, ectopic beats do not change the management of pregnancy. 

What does it mean for the baby after it is born?

The prognosis is excellent in the vast majority of cases of ectopic beats.

What other questions should I ask?

  • Are they isolated or are there many of them?
  • When should I return for a follow-up assessment?
  • What is the fetal heart rate?
  • Is the heart structurally normal?
  • What is my risk of developing more serious rhythm abnormalities?


Last updated October 2022