Premature Atrial Contractions

What are premature atrial contractions?

A premature atrial contraction (PAC) is an extra heartbeat that occurs in the heart’s upper chambers (atria), disrupting the fetus’ normal heart rhythm.

Premature atrial contractions are the most common type of fetal cardiac arrhythmias, congenital heart conditions involving an abnormal heartbeat. Arrhythmias can cause the heart to beat too fast, too slow or in this case, irregularly.

In most cases, premature atrial contractions do not cause harm to the baby and typically resolve on their own. However, it is important for any irregular fetal heartbeat to be properly evaluated, accurately diagnosed and closely monitored during pregnancy.

Premature atrial contractions are also sometimes referred to as premature atrial complexes or atrial extrasystoles (additional heartbeats).

A Disruption in the Normal Heartbeat

Normally, the heart’s upper chambers (atria) and lower chambers (ventricles) alternately contract and relax in a steady rhythm to pump blood throughout the body.

This rhythm is controlled by the sinus node, a group of cells in the atria known as the heart’s “natural pacemaker.” The sinus node generates electrical impulses that travel down through the heart causing the atria to contract and then the ventricles, pumping blood out to the lungs and body. These contractions or pumps are your heartbeat, or normal sinus rhythm.

Arrhythmias occur when something disrupts this process.

In a fetus with premature atrial contractions, an extra contraction is triggered in the atria, but not by the sinus node, interrupting the heart’s normal rhythm. This extra beat occurs prematurely, before the next normal heartbeat begins. It is typically followed by a short pause before the next regular heartbeat occurs, often more forcefully, making it seem as if the heart “skips a beat.”

In some cases, the PAC may be followed by an extra contraction in the ventricles, making it sound like intermittent extra heart beats.

How do premature atrial contractions affect my baby?

The majority of premature atrial contractions are not harmful to the baby and don’t require treatment. Most resolve over time on their own, either during pregnancy or after delivery.

While uncommon, babies with this condition are at risk of developing a more serious form of fetal arrhythmia known as fetal supraventricular tachycardia (SVT), where the heart beats too fast (0.5-1% risk of developing SVT with PACs). In rare cases where the condition progresses to SVT, the fetus may be at risk of heart failure or a life-threatening condition known as hydrops (accumulation of fluid in multiple areas of the baby’s body). Treatment with medications is necessary if this occurs.

Cause and Prevalence

Fetal arrhythmias complicate an estimated 1 to 2 percent of all pregnancies, with premature atrial contractions being the most common type.

The cause of most fetal arrhythmias is unknown. Some cases may result from an electrolyte imbalance, inflammation, medication or an inherited genetic condition. In rare cases, premature atrial contractions may develop as a result of a congenital heart defect, or structural abnormality in the fetal heart.


Premature atrial contractions may be detected when the doctor first listens to the fetal heartbeat, as early as 10 to 12 weeks of pregnancy, or during a routine prenatal ultrasound.

In some cases rhythm abnormalities may not start until later in pregnancy. Generally, the mother has no symptoms and notices no change in fetal movement.

If an abnormal heart rhythm is diagnosed, prompt referral to a fetal cardiac center for further evaluation is vital to rule out structural anomalies and ensure accurate diagnosis and proper treatment. At Texas Children’s Fetal Center, we arrange for you to visit as quickly as possible for a comprehensive assessment by a team of specialists experienced in fetal cardiac arrhythmias, including maternal-fetal medicine (MFM) physicians (OB/GYNs specializing in high-risk pregnancies), fetal and pediatric cardiologists, fetal imaging experts, and electrophysiologists (specialists in heart rhythm problems).

Additional testing may include:

  • High-resolution anatomy ultrasound to confirm the diagnosis, evaluate the condition and look for other abnormalities
  • Ultra-fast MRI for a more detailed view of fetal anatomy
  • Fetal echocardiogram to assess fetal heart structure and function, and identify the type of arrhythmia
  • Doppler ultrasound to examine blood flow patterns
  • Amniocentesis and chromosomal analysis to screen for genetic abnormalities

Our specialists will then meet with you about the results, discuss treatment recommendations and answer any questions your family has, to help you make the most informed decisions regarding your baby’s care and treatment

Treatment During Pregnancy

For cases involving isolated premature atrial contractions, where no other conditions are present, treatment is not required. The condition will usually resolve on its own during pregnancy or soon after birth.

In some cases, you may be advised to reduce caffeine intake and stress. In rare cases, if the extra heartbeats increase and come consecutively, further treatment may be needed.

Because of the risk of developing a more serious form of fetal arrhythmia, your baby’s heart rate will be closely monitored throughout pregnancy. The goal is to detect the development of fetal supraventricular tachycardia (SVT), where the heart beats too fast, before it becomes life-threatening. 


For infrequent premature atrial contractions or for cases with premature atrial contractions that resolve before birth, usually no special delivery planning or postnatal monitoring is needed. If an irregular rhythm is noted when doctors listen to the baby’s heart, an electrocardiogram (EKG) after birth may be recommended for further assessment of underlying heart rate and rhythm. Overall, the prognosis in this setting is favorable.

When premature atrial contractions are very frequent or the baby develops SVT, delivery should take place at a center with the highest quality congenital heart program, ensuring the expertise and resources required to treat fetal arrhythmias during delivery and at birth, including an advanced neonatal or cardiac intensive care unit (NICU or CICU), if needed. In cases of SVT, the infant may require medications following birth to treat the arrhythmia.

Our Fetal Center team works closely with the nationally recognized experts at Texas Children’s Heart Center for seamless access to the critical care services and specialists your child may need after delivery, avoiding the need for transfers. Here, the pediatric specialists treating your baby have been an integral part of their care team since before birth.

Treatment After Birth

Treatment needs after birth vary based on each baby’s arrhythmia and any associated conditions.

In most cases, babies with premature atrial contractions have a good prognosis with no long-term issues.

Your baby’s care team after birth may include:

Why Texas Children’s Fetal Center?

  • A single location for expert maternal, fetal and pediatric care. At Texas Children’s Hospital, mothers and babies receive the specialized care required for the diagnosis and treatment of congenital heart conditions all in one location, for highly coordinated care and treatment planning.
  • A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine specialists, fetal imaging experts, fetal and pediatric cardiologists, and neonatologists who work in concert to care for you and your baby every step of the way, using proven protocols we’ve developed over the years. With their combined expertise and unified approach, this team offers the best possible care for pregnancies involving fetal cardiac arrhythmias.
  • We care for your child’s needs at every stage of life. Our comprehensive approach starts with your first prenatal visit and continues through delivery, postnatal care, childhood and beyond, as needed, thanks to one of the nation’s leading teams of fetal and pediatric heart specialists.

Texas Children’s Hospital – #1 in the Nation for Pediatric Cardiology and Heart Surgery

Our Fetal Cardiology Program is a collaboration between Texas Children’s Fetal Center and Texas Children’s Heart Center, ranked #1 in the nation for pediatric cardiology and heart surgery by U.S. News & World Report for consecutive years, with outcomes among the best in the country.

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Additional Resources

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Research and Clinical Trials

Texas Children’s, together with our partner institution Baylor College of Medicine, constantly strives to seek new and better treatments for babies with congenital heart conditions.

For more information, please contact the Cardiovascular Clinical Research Core at 832-826-2064 or email

Learn more about our fetal cardiology research.

For more information or to schedule an appointment,

call Texas Children’s Fetal Center at 832-822-2229 or 1-877-FetalRx (338-2579) toll-free.

Our phones are answered 24/7. Immediate appointments are often available.