Atrial Fibrillation


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is atrial fibrillation?

Atrial fibrillation (AF; A-fib) is a common type of heart arrhythmia that is characterized by disorganized activation of the heart muscle cells comprising the muscular wall of the left and right atria, the hearts two upper chambers. The job of the atria is to receive blood that returns to the heart and pump it into the hearts lower chambers, the ventricles. Normally, the right atrium receives blood that has finished circulating through the body and sends the blood to the right ventricle, which pumps it into the lungs. Blood returning from the lungs arrives in the left atrium, which then pumps it into the left ventricle whose job is to pump the blood to the body. In order to pump blood into the ventricles, the atrial muscle cells must beat in unison, which can happen only if the cells activate simultaneously. Since the simultaneous activation does not happen in AF, the two atria merely quiver instead of pumping. Typically, when AF occurs in pregnancy, it happens in episodes (it starts and stops), which can go unnoticed, but the woman usually experiences symptoms, particularly palpitations (a sensation of the heartbeat in the chest or sensation of beat irregularity), fatigue, shortness of breath, and chest pain or discomfort.

How common is atrial fibrillation during pregnancy?

AF is present in about 0.5 1 percent of adults. It is more common in older people, but half a century ago, the condition was nevertheless common enough to be present at the beginning of 8 percent of pregnancies and starting as a new condition in 2.5 percent of pregnant women.  A recent study found AF to occur at much lower rates (42 AF cases existing at the onset of pregnancy per 100,000 pregnancies; 17 cases of AF starting during pregnancy per 100,000), but an increasing number of women are getting pregnant at older ages. Furthermore, the risk of developing AF is elevated in people suffering from diabetes mellitus and obesity, both of which are occurring in an increasing number of people, including women of reproductive age. Risk factors for developing AF include smoking, hyperthyroidism (an overactive thyroid), and excessive consumption of alcohol, so AF during pregnancy is a fairly realistic scenario.

How is atrial fibrillation diagnosed?

AF is diagnosed by way of electrocardiography (ECG, sometimes abbreviated EKG), and also through Holter monitoring. Both are non-invasive procedures that work through electrodes that are attached to your skin. In ECG, electrodes are attached on your arms, leg, and chest, and in some cases, additional sites, to provide your doctor with detailed information on the hearts electrical activity from numerous angles in order to detect problems in different regions of the heart. This is done in the doctors office or the hospital. Holter monitoring is similar to ECG, but you are fitted with a device that you wear for a day or more while you go about your normal activities. Various types of Holter monitors are available with varying numbers of electrodes, depending on how much detail is needed about different parts of your heart. In all cases, however, unlike ECG, the Holter monitor records data constantly and transmits that data to your doctor (or the data is downloaded when you return to the doctor). Consequently, if some electrical event happens just once in a while, your doctors can see it.

Doctors will also run a test called echocardiography and may do exercise testing in which you are asked to exercise while ECG or echocardiography is being recorded. Blood samples will be taken for tests such as thyroid function (to see if a thyroid condition is causing your heart problem), cardiac enzymes (to rule out a myocardial infarction [MI] – a heart attack in which part of the heart tissue is damaged), and to look for electrolyte imbalances that also may affect the heart.

Does AF cause problems during pregnancy?

An attack of AF can lead you to feel light-headed and dizzy and possibly faint. It also can lead to a stroke, an MI, and heart failure, all of which can cause long-term disability or death.

Does AF during pregnancy cause problems for the baby?

An AF episode that causes an MI or heart failure can put the health and life of the developing baby at risk by causing a reduction of blood circulation through the uterus and placenta.

What to consider about taking medications when you are pregnant or breastfeeding:

  • The risks to yourself and your baby if you do not treat the AF
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat my atrial fibrillation during pregnancy?

The medication strategy in AF includes the need to prevent a stroke (a blood clot in the brain) in those women who are considered to be at-risk based on a calculation of what is called the CHA2DS2-VASc score.  Stroke is caused by the AF producing an embolism (traveling clot) that reaches the brain. The gold standard way to prevent this is with a drug called warfarin. This thins the blood by interfering with vitamin K, but warfarin cannot be given during pregnancy (especially at the end of the first trimester, but doctors generally avoid it throughout pregnancy) since it passes through the placenta and can cause the developing baby’s brain to bleed. If you are taking warfarin before pregnancy, or if AF develops as a new condition and your doctor determines that you are at risk for a stroke, the treatment of choice is called low molecular weight heparin (LNWH), which is considered fairly safe for the baby. There are a handful of new medications entering clinical use that can replace warfarin, but studies are needed for their effects in pregnancy.

To calm the heart, doctors often give drugs called beta-blockers examples are propranolol, metoprolol, and labetalol. Anti-arrhythmia medication, such as flecainide, propafenone, and amiodarone, are often indicated as well, but there is uncertainty about the pregnancy safety of many of these medications.

Who should NOT stop taking medication for AF during pregnancy?

If you need a blood thinner such as LMWH because of the CHA2DS2-VASc score that your doctor has calculated, you must take it to avoid the possibility of suffering a stroke. Similar calculations can be made surrounding the issue of beta-blockers. The risk-benefit tradeoff is more difficult to estimate for anti-arrhythmia drugs. With all medications, however, the need in AF works on a case-by-case basis, especially in the setting of pregnancy.

What should I know about choosing a medication for my AF during pregnancy?

You may find Pregistrys expert reports about the individual medications used to treat AF here. Additional information can also be found in the sources listed at the end of this report.

What should I know about taking a medication for my AF when I am breastfeeding?

LMWH is considered safe in breastfeeding mothers.

What alternative therapies besides medications can I use to treat atrial fibrillation during pregnancy?

AF is often treated effectively, with a permanent cure, with a technique called ablatio
n, in which a specially-trained cardiologist guides instruments through tubes through your blood vessels to the site of the ectopic pacemaker and destroys it. This procedure can be done safely during pregnancy. In the event that your heartbeat becomes unstable, doctors may need to perform a procedure called synchronized cardioversion, in which an electric shock is supplied to the heart at a specific time in the heartbeat cycle.

What can I do for myself and my baby when I have atrial fibrillation during pregnancy?

Cooperate with your physicians. Consider procedures, such as ablation, as a means of ending the problem. If medications are recommended to stabilize your condition, keep in mind that this is generally safe.

Resources for atrial fibrillation in pregnancy:

For more information about atrial fibrillation during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or check the following links:


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Last Updated: 19-02-2020
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

Medications for Atrial Fibrillation