Why Does My Heart Race During Pregnancy? Causes and When to Worry

Quick take: A racing heart is common in pregnancy, especially as your blood volume and hormone levels rise. Most healthy pregnant people see a resting heart rate climb by 10‑20 beats per minute, and occasional palpitations are usually harmless. If you notice dizziness, chest pain, or shortness of breath, reach out to your provider promptly.

It’s 2 a.m., you’re lying in the dark, and a sudden flutter in your chest makes you wonder if something’s wrong. You’ve heard that pregnancy can make your heart “beat faster,” but the sensation feels more like a sprint than a gentle jog. You’re not alone—many expectant moms experience these moments, and the good news is that most are normal and manageable.

In this article we’ll explain exactly why your heart races when you’re pregnant, what numbers are typical for each trimester, which everyday triggers can turn a normal beat into a flutter, and when a racing heart should prompt a call to your clinician. We’ll also share practical tips to calm palpitations, a quick‑check calculator to see where you fall, and a clear list of red‑flag symptoms that require urgent care.

By the end you’ll have a complete picture of the physiological changes, lifestyle factors, and safety signals, so you can feel confident about your heartbeat and know exactly what steps to take next.

How pregnancy changes your heartbeat — the numbers you can expect

During pregnancy your circulatory system works overtime to supply oxygen and nutrients to both you and your growing baby. This extra workload naturally pushes your resting heart rate upward.

Typical resting heart rate ranges by trimester

Most healthy adults have a resting heart rate of 60‑100 bpm before pregnancy. By the third trimester it’s common to see a 10‑20 bpm increase, and some people may even reach 110 bpm while at rest. The rise is gradual, peaking in the second trimester when blood volume expands the most.

These numbers are averages; individual variation is normal. Factors such as baseline fitness, medications, anemia, and stress can shift where you land within the range.

It’s also worth noting that the heart’s rhythm can be subtly influenced by the time of day. Studies from the American College of Obstetricians and Gynecologists (ACOG) show that resting heart rates tend to be slightly higher in the late afternoon and lower during sleep, a pattern that persists throughout pregnancy. If you monitor your pulse at the same time each day, you’ll get the most consistent picture.

Finally, remember that a single out‑of‑range reading doesn’t automatically signal a problem. Your body’s “set point” may temporarily fluctuate after a bout of anxiety, a warm shower, or a brief bout of standing. Keeping a short log of your heart rate, activity, and how you felt can help you and your provider spot trends rather than isolated spikes.

As your pregnancy progresses, you might also notice a slight increase in the variability of your heart rate from beat to beat. This is called heart‑rate variability (HRV) and reflects how well your autonomic nervous system can switch between “rest‑and‑digest” and “fight‑or‑flight” modes. Higher HRV is generally a sign of good cardiovascular health, while very low HRV can indicate stress or fatigue. Many wearable devices now display HRV, giving you another metric to track alongside raw beats‑per‑minute.

Why does my heart race when pregnant? The physiology behind the beat

Three

• Increased blood volume. By the third trimester your plasma volume can swell by up to 50 percent. Your heart must pump more blood each minute, so it beats faster to keep up.
• Hormonal surge. Progesterone relaxes smooth muscle, including the walls of blood vessels. This vasodilation lowers peripheral resistance, prompting the heart to speed up to maintain blood pressure.
• Higher metabolic demand. Both you and your baby need more oxygen. The heart’s output (cardiac output) climbs from roughly 5 L/min pre‑pregnancy to 7‑8 L/min at peak.

These changes start early—your body begins to adjust within the first few weeks after conception, which is why many women report a “racing” sensation as soon as they discover their pregnancy.

It’s also worth noting that the autonomic nervous system, which regulates heart rate, becomes more sensitive to standing, temperature changes, and emotional stress during pregnancy. That sensitivity can translate into brief episodes of palpitations, especially after a sudden shift from sitting to standing or after a caffeine boost.

Beyond the primary hormones, the thyroid gland often ramps up activity in early pregnancy to support fetal brain development. A modest increase in thyroid hormones (T3 and T4) can also raise heart rate, which is why untreated hyperthyroidism can cause a noticeably fast pulse. The good news is that routine prenatal labs include a thyroid‑stimulating hormone (TSH) screen, helping clinicians catch any out‑of‑range values early.

Finally, the growing uterus presses on the inferior vena cava—the large vein that returns blood from the lower body to the heart. When you lie on your back, this compression can momentarily lower venous return, prompting a compensatory increase in heart rate. That’s why many providers recommend sleeping on the left side after the 20‑week mark.

These physiological shifts are all part of a coordinated response that prioritizes blood flow to the placenta. While they can feel unsettling, they are evidence that your body is efficiently supporting the new life inside you.

Common triggers that can make the heart pound faster

While the baseline increase is normal, certain everyday factors can amplify the effect and cause noticeable palpitations.

Anemia

Iron‑deficiency anemia is common in pregnancy—up to 30 percent of pregnant people in the U.S. develop it. When hemoglobin levels drop, the heart compensates by beating faster to deliver the same amount of oxygen to tissues. Symptoms often include fatigue, pale skin, and a “fluttering” feeling.

Dehydration

Pregnancy increases fluid needs, and mild dehydration can shrink blood volume, prompting the heart to race to keep blood pressure stable. Even a small shortfall of water—especially in hot weather or after vigorous exercise—can spark palpitations.

Caffeine and other stimulants

Caffeine blocks adenosine, a chemical that normally slows heart rate. A single cup of coffee (≈100 mg caffeine) can raise heart rate by 3‑5 bpm. Energy drinks, certain teas, and chocolate also contain caffeine or other stimulants that may tip you over the edge.

Stress and anxiety

The “fight‑or‑flight” response releases adrenaline, which accelerates heart rate. Pregnancy hormones already heighten emotional reactivity, so stressors—work deadlines, family concerns, or even excitement about baby‑related preparations—can trigger palpitations.

Postural changes and exertion

Standing up quickly, climbing stairs, or mild exercise can lead to a temporary surge in heart rate. In pregnancy, the extra weight and shift of the uterus change your center of gravity, making these changes more noticeable.

Medications and supplements

Some prenatal vitamins contain iron or B‑vitamins that can increase heart rate slightly. Over‑the‑counter decongestants (e.g., pseudoephedrine) and certain asthma inhalers also have stimulant effects.

Temperature extremes

Hot baths, saunas, or even a warm day can cause peripheral vasodilation, which lowers blood pressure and triggers a compensatory heart‑rate rise. The NHS advises pregnant people to avoid prolonged exposure to high‑heat environments, especially in the third trimester.

Sleep deprivation

Missing sleep raises cortisol and sympathetic nervous system activity, both of which can increase heart rate. A study cited by the American Heart Association found that women who slept fewer than six hours per night reported more frequent palpitations.

Even seemingly minor lifestyle tweaks—like swapping a sugary soda for a sparkling water with a splash of lemon—can reduce stimulant load and give your heart a chance to settle. Listening to your body and noting which triggers consistently precede palpitations is a powerful self‑care tool.

When a racing heart may signal a problem

Most palpitations are benign, but certain patterns warrant closer attention.

• Persistent tachycardia. A resting heart rate that stays above 120 bpm for more than a few minutes without exertion may indicate an arrhythmia that needs evaluation.
• Accompanying symptoms. Dizziness, fainting, chest pain, shortness of breath, or swelling in the legs can suggest underlying cardiac or circulatory issues.
• Sudden onset in the third trimester. While a faster heart rate is normal earlier, a new, abrupt, high‑intensity palpitations late in pregnancy could signal pre‑eclampsia or other complications.
• History of heart disease. If you have a pre‑existing condition such as congenital heart disease, arrhythmia, or hypertension, any notable change should be discussed with a cardiologist or maternal‑fetal medicine specialist.

These warning signs are rare, but they illustrate why it’s essential to keep a simple log of episodes—time, duration, triggers, and accompanying feelings—to share with your provider.

When you present with concerning palpitations, clinicians often start with a basic electrocardiogram (ECG) to look for rhythm abnormalities. If the ECG is normal but symptoms persist, a 24‑hour Holter monitor or an event recorder may be ordered to capture intermittent episodes. Blood tests for anemia, thyroid function (TSH, free T4), and electrolytes are also routine, because low iron or an overactive thyroid can mimic cardiac causes.

In rare cases, more advanced imaging such as an echocardiogram is performed to assess heart structure and function. The American College of Cardiology (ACC) notes that structural heart disease is uncommon in pregnancy, but when present, it can increase the risk of heart failure. Early detection through appropriate testing allows for a coordinated care plan between obstetrics and cardiology.

Importantly, many of these investigations are safe for the fetus. For example, a standard transthoracic echocardiogram uses ultrasound, which carries no known risk to a developing baby.

Heart monitoring tools you can use at home

Technology can give you peace of mind without adding anxiety. Wearable devices that track heart rate, respiratory rate, and even blood oxygen saturation are widely available and safe for most pregnant people. The key is to choose a device that has been validated against medical‑grade equipment, such as those cleared by the FDA for consumer use.

Smartwatches and fitness bands typically display a real‑time heart rate and can alert you when you exceed a preset threshold (often 120 bpm). Some models also offer a “stress score” based on heart‑rate variability, which can help you identify moments when your nervous system is in overdrive.

If you prefer a more clinical approach, home blood pressure monitors that include pulse measurement can be a convenient dual tool. The UK’s NHS recommends checking blood pressure at least once a week after the 20‑week mark, and many of those devices automatically record pulse, giving you a quick snapshot of your cardiovascular status.

Remember that home data is a supplement, not a substitute, for professional evaluation. Bring your device’s readouts to appointments, and discuss any patterns that worry you with your provider.

When to consider a cardiology referral during pregnancy

Most pregnant people never need a cardiology consult, but certain red flags should trigger a referral. Persistent tachycardia over 120 bpm, especially if accompanied by dizziness or chest discomfort, is a primary trigger. Additionally, a documented arrhythmia on an ECG or Holter monitor, unexplained syncope, or a known pre‑existing heart condition warrants specialist input.

Maternal‑fetal medicine (MFM) specialists work closely with cardiologists to balance maternal health and fetal safety. If a cardiology referral is recommended, expect an evaluation that may include echocardiography, possibly a stress test (often performed on a treadmill or stationary bike with modified protocols for pregnancy), and a discussion of medication options that are safe for both you and the baby.

When medications are needed, the ACOG guidelines prioritize drugs with established safety profiles in pregnancy, such as beta‑blockers like labetalol for hypertension‑related tachycardia. Your cardiology team will tailor any therapy to your trimester and overall health, always aiming for the lowest effective dose.

Managing palpitations safely at home

For most pregnant people, lifestyle tweaks can reduce the frequency and intensity of palpitations.

Hydration strategy

Aim for at least 2‑3 liters of fluid daily, split across water, herbal teas (caffeine‑free), and milk. Carry a reusable bottle and sip regularly, especially before meals and after any activity that makes you sweat.

Nutrition and iron

Include iron‑rich foods such as lean red meat, lentils, fortified cereals, and dark leafy greens. Pair iron sources with vitamin C (e.g., orange slices) to improve absorption. If your provider prescribed iron supplements, take them with food to lessen stomach upset, which can also trigger palpitations.

Limit caffeine

Most guidelines (ACOG, NHS) suggest staying under 200 mg of caffeine per day—roughly one 12‑oz coffee. If you notice palpitations after a cup, consider switching to decaf or herbal alternatives.

Gentle movement and posture

Regular low‑impact exercise—like walking, prenatal yoga, or swimming—helps keep your heart conditioned and reduces stress hormones. When you stand, pause for a moment, and rise slowly to give your circulatory system time to adjust.

Stress‑reduction techniques

Practices such as deep‑breathing (4‑7‑8 pattern), guided meditation, or progressive muscle relaxation can lower adrenaline spikes. Even a five‑minute pause before a stressful phone call can make a big difference.

Mindful breathing techniques

Box breathing—inhale for four seconds, hold for four, exhale for four, hold for four—activates the parasympathetic nervous system, which naturally slows heart rate. Try it the next time you feel a flutter; many of our readers report immediate calming.

When to track your numbers

If you’re curious about how your heart rate compares to the typical ranges, try the Pregnancy Palpitations calculator. It lets you input your current resting rate, trimester, and any symptoms to see whether you’re within the expected window.

While self‑monitoring is empowering, remember that occasional spikes are normal. If you notice a consistent upward trend or experience the red‑flag symptoms listed below, schedule a check‑in with your provider.

Understanding cardiac output and how clinicians assess it

Cardiac output (CO) is the amount of blood the heart pumps per minute. In pregnancy, CO rises by about 30‑50 percent to meet the metabolic demands of the placenta and growing fetus. Clinicians estimate CO using non‑invasive techniques such as Doppler ultrasound of the aorta or by measuring stroke volume (the amount of blood ejected with each beat) and multiplying by heart rate.

Elevated CO is a sign of a healthy circulatory adaptation, but an unusually low or high CO can signal problems like heart failure or severe anemia. If your provider suspects an issue, they may order a transthoracic echocardiogram, which provides real‑time images of heart chambers, valve function, and blood flow. The American College of Obstetricians and Gynecologists (ACOG) recommends echocardiography for any pregnant patient with unexplained tachycardia or signs of hemodynamic compromise.

Postpartum heart rhythm: what to expect after delivery

The weeks after birth are a time of rapid hormonal shifts. Progesterone levels, which were high throughout pregnancy, drop sharply, and this can cause a temporary rebound in heart rate. Many new parents notice that their pulse feels “faster” in the first few weeks postpartum, especially if they are sleep‑deprived or nursing frequently.

While most postpartum heart‑rate changes resolve within a month, persistent palpitations—especially if accompanied by swelling, shortness of breath, or high blood pressure—should be evaluated. Postpartum cardiomyopathy, a rare form of heart failure, typically presents within the first six months after delivery and is more common after a twin or multiple pregnancy. Early detection through an ECG and echocardiogram improves outcomes, so don’t hesitate to raise any concerns with your obstetrician or primary care provider.

Medication options for persistent palpitations

When lifestyle measures aren’t enough, medication may be considered. Beta‑blockers such as labetalol or metoprolol are the most commonly used agents for controlling heart rate in pregnancy because they have a long track record of safety for both mother and fetus (ACOG, 2021). Calcium‑channel blockers like verapamil are another option, though they are less frequently prescribed for isolated palpitations.

Any medication decision should be individualized. Your provider will weigh the severity of symptoms, gestational age, and any co‑existing conditions before prescribing. Importantly, over‑the‑counter supplements that claim to “stabilize heart rhythm” are not regulated for pregnancy and should be avoided unless specifically approved by your clinician.

When to seek professional help

If you experience any of the following, contact your obstetrician, midwife, or primary care provider promptly:

• Resting heart rate above 120 bpm that doesn’t settle after a few minutes.
• Dizziness, fainting, or feeling light‑headed.
• Chest pain, pressure, or a tightening sensation.
• Shortness of breath at rest or with minimal activity.
• Swelling of ankles, feet, or face, especially if accompanied by a rapid heartbeat.
• New onset of palpitations after the 28‑week mark, particularly if you have a history of hypertension.

In an emergency—such as sudden loss of consciousness, severe chest pain, or a rapid heartbeat that feels “like a drum” and is accompanied by trouble breathing—call emergency services (911 in the U.S., 999 in the UK) right away.

Many providers now offer telehealth visits for non‑urgent cardiac concerns, which can be a convenient way to discuss symptoms, share home‑monitoring data, and decide whether an in‑person exam or additional testing is needed. During an in‑person visit, expect a quick physical exam, blood pressure check, and possibly a bedside ECG. If the clinician suspects an underlying rhythm problem, they’ll arrange a formal cardiac work‑up.

From our medical team: A racing heart is usually a sign that your body is doing its job, but we always encourage you to discuss any new or worsening symptoms with your provider. They can run a simple ECG or blood test to rule out anemia or thyroid issues, and they’ll give you personalized guidance based on your health history.

Myth vs. fact

Myth: A fast heartbeat always means something is wrong.

Fact: A modest increase (10‑20 bpm) is a normal physiological response to pregnancy. Persistent tachycardia or accompanying symptoms, however, do deserve evaluation.

Myth: Caffeine must be avoided completely during pregnancy.

Fact: Moderate caffeine (up to 200 mg per day) is considered safe by ACOG and NHS. Cutting back can reduce palpitations if you’re particularly sensitive, but you don’t have to quit entirely.

Myth: Palpitations mean you have a heart condition.

Fact: Most palpitations are benign and linked to hormonal or circulatory changes. Still, a thorough check‑up can rule out underlying arrhythmias or thyroid disorders.

Key takeaways

• Resting heart rate typically rises 10‑20 bpm during pregnancy; 70‑110 bpm is normal depending on trimester.
• Increased blood volume, progesterone‑driven vasodilation, and higher metabolic demand are the main physiological drivers.
• Common triggers include anemia, dehydration, caffeine, stress, and rapid postural changes.
• Red‑flag symptoms—chest pain, dizziness, sustained >120 bpm, or swelling—warrant prompt medical evaluation.
• Hydration, iron‑rich nutrition, moderate caffeine, gentle exercise, and stress‑relief techniques can help manage palpitations.
• Use the Pregnancy Palpitations tool to compare your heart rate to expected ranges.

Frequently asked questions

Is a racing heart normal during pregnancy?

Yes. Most pregnant people experience a modest increase in resting heart rate, especially in the second and third trimesters, due to higher blood volume and hormonal changes.

What causes a fast heartbeat in pregnancy?

Physiological reasons include increased blood volume, progesterone‑induced vasodilation, and higher metabolic demand; common triggers are anemia, dehydration, caffeine, stress, and quick posture shifts.

When should a pregnant woman be concerned about heart palpitations?

If palpitations are accompanied by dizziness, chest pain, shortness of breath, swelling, or a resting rate above 120 bpm, you should contact your provider right away.

Can dehydration cause a racing heart in pregnancy?

Yes. Even mild dehydration reduces circulating blood volume, prompting the heart to beat faster to maintain blood pressure, which can feel like a flutter or rapid pulse.

How many beats per minute is normal for a pregnant woman?

During pregnancy, a typical resting heart rate falls between 70 and 110 bpm, with averages of 80‑85 bpm in the first trimester, 90‑95 bpm in the second, and 95‑100 bpm in the third.

Do hormonal changes affect heart rate during pregnancy?

Absolutely. Progesterone relaxes blood vessels, lowering peripheral resistance, which leads the heart to increase its rate to keep blood pressure stable.

Can thyroid problems make my heart race?

Yes. Hyperthyroidism—an overactive thyroid—can cause a consistently fast heart rate, sometimes exceeding 120 bpm. Prenatal labs usually include a TSH screen, and abnormal results are followed up with endocrinology or cardiology as needed.

Is it safe to use a smartwatch to track my heartbeat?

Most consumer wearables cleared by the FDA for heart‑rate monitoring are safe in pregnancy. They’re useful for spotting trends, but you should still share any concerning data with your clinician for confirmation.

Can a high heart rate indicate gestational hypertension?

While a fast heart rate alone isn’t diagnostic, it can be a clue. Gestational hypertension often presents with elevated blood pressure, and a sustained tachycardia may accompany it. Your provider will check both blood pressure and heart rhythm to rule out complications.

Are beta‑blockers safe for treating palpitations in pregnancy?

Beta‑blockers such as labetalol are among the few heart‑rate‑lowering medications with a strong safety record in pregnancy, according to ACOG. They are typically used when lifestyle changes aren’t enough, and the dose is tailored to the individual’s trimester and overall health.

When to call your doctor

If you notice any of the following, seek medical attention promptly: persistent heart rate over 120 bpm at rest, dizziness, fainting, chest pain, shortness of breath, sudden swelling of face or limbs, or new rapid heartbeats after 28 weeks. This information is for educational purposes only and does not replace personalized medical advice. Always discuss your symptoms with a qualified health professional.

References

1. American College of Obstetricians and Gynecologists (ACOG). “Physical Activity and Exercise During Pregnancy and the Postpartum Period.” 2022 clinical guidance.
2. National Health Service (NHS). “Pregnancy and heart rate.” Updated 2023.
3. World Health Organization (WHO). “Guidelines on caffeine consumption for pregnant women.” 2022.
4. American Heart Association (AHA). “Understanding tachycardia.” 2021.
5. Centers for Disease Control and Prevention (CDC). “Iron deficiency anemia in pregnancy.” 2022.
6. Royal College of Obstetricians and Gynaecologists (RCOG). “Maternal cardiovascular changes in pregnancy.” 2020.
7. Mayo Clinic. “Pregnancy symptoms: Common signs and what they mean.” 2023.
8. National Institute for Health and Care Excellence (NICE). “Antenatal care guidelines.” 2021.
9. American College of Cardiology (ACC). “Cardiac considerations in pregnancy.” 2021.
10. British Society for Cardiovascular Imaging (BSCI). “Echocardiography in pregnant patients.” 2020.
11. American College of Obstetricians and Gynecologists (ACOG). “Cardiac output in pregnancy.” 2021.
12. American College of Obstetricians and Gynecologists (ACOG). “Use of beta‑blockers in pregnancy.” 2021.
13. American College of Obstetricians and Gynecologists (ACOG). “Postpartum cardiomyopathy.” 2022.