Atrial Fibrillation During Pregnancy: Risks, Symptoms & Management

Oct, 4 2025

Key Takeaways

• Atrial fibrillation (AFib) occurs in about 1 in 1,000 pregnancies and raises the chance of stroke and heart failure for the mother.
• Uncontrolled AFib can cause fetal growth restriction, preterm birth, and low birth weight.
• Rate‑control drugs (beta‑blockers, calcium‑channel blockers) are first‑line; rhythm‑control (cardioversion, ablation) is reserved for severe cases.
• Anticoagulation with low‑molecular‑weight heparin (LMWH) is recommended throughout pregnancy; warfarin and DOACs are avoided.
• Close multidisciplinary follow‑up-including obstetrics, cardiology, and anesthesiology-is essential from diagnosis to postpartum.

Understanding Atrial Fibrillation in Pregnancy

When we talk about Atrial Fibrillation is an irregular, often rapid heart rhythm that originates in the upper chambers of the heart (atria). In a pregnant woman, the heart already works harder-blood volume rises 40‑50%, cardiac output climbs 30‑50%, and hormone shifts increase excitability. Those physiologic changes can turn a borderline rhythm into full‑blown AFib.

Pregnancy is the state of carrying a developing embryo or fetus inside the uterus, typically lasting about 40 weeks. While most pregnancies are uncomplicated, underlying heart disease or new‑onset AFib adds a layer of risk that requires careful monitoring.

How Common Is AFib During Pregnancy?

Large registries from the United States and Europe estimate an incidence of roughly 0.1% (1 in 1,000) among all pregnancies. The odds rise to 1‑2% in women with pre‑existing structural heart disease, hypertension, or obesity. Age matters too-women over 35 have a noticeably higher risk, reflecting the general population trend.

Maternal Risks: What Can Happen to Mom?

AFib isn’t just an uncomfortable flutter; it can have serious downstream effects:

• Stroke: Irregular atrial contraction can let clots form and travel to the brain. Pregnant women have a hypercoagulable state, so the baseline stroke risk is already higher.
• Heart Failure: Rapid rates (often >120bpm) reduce filling time, leading to reduced output and, in severe cases, pulmonary edema.
• Maternal Mortality: Though rare, uncontrolled AFib combined with other comorbidities can be fatal.

Data from the 2023 AHA/ACC Pregnancy Registry show that women with AFib have a 4‑fold increase in ICU admission compared with uncomplicated pregnancies.

Fetal Risks: How the Baby Is Affected

When the mother’s circulation is unstable, the placenta can suffer. The main fetal concerns are:

• Intrauterine growth restriction (IUGR) due to reduced uteroplacental blood flow.
• Preterm labor triggered by maternal stress or medication side‑effects.
• Low birth weight and occasional NICU admission.

Importantly, the arrhythmia itself does not cross the placenta, but the treatments and maternal hemodynamics do.

Diagnosing AFib in a Pregnant Patient

Symptoms often overlap with normal pregnancy: palpitations, shortness of breath, and fatigue. However, a persistent irregular pulse or an ECG showing absent P‑waves and irregular R‑R intervals confirms AFib. A 12‑lead ECG is safe in pregnancy; radiation is not a concern. If the rhythm is intermittent, a Holter monitor or event recorder can be used.

Management Overview: Rate vs. Rhythm Control

Two strategies dominate:

1. Rate Control: Keep the heart rate below 100bpm at rest. Beta‑blockers (e.g., metoprolol) are the go‑to drugs because they are well‑studied in pregnancy. Non‑dihydropyridine calcium‑channel blockers (verapamil, diltiazem) are alternatives if beta‑blockers cause severe bradycardia or hypotension.
2. Rhythm Control: Try to restore normal sinus rhythm. Electrical cardioversion is safe after the first trimester, while anti‑arrhythmic drugs (e.g., flecainide) are generally avoided due to limited safety data.

The choice hinges on symptom severity, duration of AFib, and comorbidities.

Anticoagulation: Keeping Clots at Bay

Pregnancy is a hyper‑coagulable state, so anticoagulation is a cornerstone of therapy. The hierarchy is clear:

• Low‑Molecular‑Weight Heparin (LMWH) is the first‑line agent. It does not cross the placenta and has a predictable dose‑response.
• Unfractionated Heparin (UFH) may be used during labor when rapid reversal is needed.
• Warfarin and Direct Oral Anticoagulants (DOACs) are contraindicated because they cross the placenta and increase fetal bleeding risk.

Target anti‑Xa levels for therapeutic LMWH in pregnancy are 0.6‑1.0IU/mL (peak, 4hours post‑dose). Dose adjustments are required as weight changes.

Medication Safety Table

Procedural Options When Medication Isn’t Enough

Electrical Cardioversion is a controlled, synchronized shock to the heart that restores normal rhythm. In pregnancy, it’s considered safe after 12 weeks gestation because fetal exposure to the brief electrical field is negligible. Fetal monitoring before and after the procedure is recommended.

Catheter Ablation is a minimally invasive technique that destroys the tissue triggering arrhythmia. It’s usually postponed until postpartum unless the mother faces life‑threatening tachycardia unresponsive to drugs. If absolutely necessary, a zero‑fluoroscopy approach using intracardiac echocardiography can limit radiation.

Delivery Planning and Postpartum Care

Women with AFib should deliver in a tertiary center with cardiology backup. Mode of delivery (vaginal vs. C‑section) is dictated by obstetric indications, not the arrhythmia itself.

During labor, a continuous ECG strip is useful. LMWH is stopped 12hours before induction or C‑section, and UFH is switched on if the estimated blood loss is high. After delivery, anticoagulation transitions back to warfarin (if long‑term) or a DOAC (once breastfeeding considerations are addressed).

Post‑partum AFib can persist or recur. Close follow‑up for at least 6months is advised, with repeat echocardiography to assess structural changes that may have developed during pregnancy.

Practical Checklist for Clinicians and Patients

• Obtain baseline ECG and echocardiogram at diagnosis.
• Start rate‑control beta‑blocker (metoprolol) unless contraindicated.
• Initiate therapeutic LMWH; adjust dose by anti‑Xa levels.
• Arrange multidisciplinary team: obstetrician, cardiologist, anesthesiologist, hematologist.
• Plan for continuous cardiac monitoring during labor.
• Switch to UFH 12h before delivery; resume LMWH 24h postpartum if bleeding is controlled.
• Schedule a 6‑week postpartum cardiac review to decide on long‑term rhythm strategy.