A heart that beats faster during pregnancy is usually a sign the body is doing its job. The heart takes on far more work to supply the baby and placenta, so a higher resting pulse is built into a healthy pregnancy.1PubMed Central. Physiological changes in pregnancy Over nine months, a rise of about 10 to 15 beats per minute, often into the high 70s or 80s, is normal.
The same faster heartbeat can also be how dehydration, low iron, a thyroid problem or, rarely, heart trouble first shows up.2Tampa General Hospital. Heart Rate During Pregnancy A resting rate over 100 that doesn’t settle, palpitations lasting more than 30 seconds, or a fast heartbeat with chest pain, breathlessness or fainting calls for a call to your doctor or emergency care.
How Much Your Pulse Normally Rises
Before pregnancy, a typical resting pulse sits around 65 to 66 beats per minute.3Harvard T.H. Chan School of Public Health. Understanding exercise patterns and heart rate throughout pregnancy It climbs steadily as pregnancy goes on and peaks in the third trimester at about 77 beats per minute, roughly 8 weeks before delivery.4Harvard T.H. Chan School of Public Health. Understanding exercise patterns and heart rate throughout pregnancy The rate falls again after delivery.5Harvard T.H. Chan School of Public Health. Understanding exercise patterns and heart rate throughout pregnancy Carrying twins pushes it higher: in one comparison, twin pregnancies averaged about 91 beats per minute at rest versus 81 for single babies.6PubMed. Cardioautonomic control in healthy singleton and twin pregnancies
The reason is mostly about blood vessels. Early in pregnancy they relax and widen, which lowers resistance to blood flow by about a quarter to a third.7PubMed Central. Physiological changes in pregnancy To keep blood pressure steady, the heart pumps more, about 40% more blood per minute by the end, and up to 45%.8PubMed Central. Physiological changes in pregnancy9PubMed. Alterations in Vessel Hemodynamics Across Uncomplicated Pregnancy By 8 weeks it is already pumping 20% more.10PubMed Central. Physiological changes in pregnancy Early on, most of that gain comes from a bigger volume with each beat. Later, more of it comes from a faster rate.11PubMed. Alterations in Vessel Hemodynamics Across Uncomplicated Pregnancy
To take a resting pulse properly, sit or lie on your side quietly for five minutes first. Count beats at the wrist or neck for 30 seconds and double it. Don’t measure right after climbing stairs, a coffee or a stressful moment. Taking readings at the same time of day over several days shows you your own baseline.
That baseline matters more than any single figure. A fit person starting at 55 may reach only the high 60s, which is still a normal rise. Someone starting at 75 may sit in the high 80s with nothing wrong. A sudden jump from your usual pattern tells you more than one number does.
The averages above come from groups of women, so about half of healthy women will sit above or below them, and your own pre-pregnancy number is the better yardstick. Your pulse also moves through the day, lower after rest or sleep and higher after meals, standing up or in a warm room. If you never checked before pregnancy, first-trimester readings can serve as a starting point, though they already include some rise.
When a Fast Heartbeat Needs a Call or Emergency Care
Call your doctor if your resting heart rate is above 100 beats per minute.12UNM Health. How Pregnancy Affects the Heart: Normal Symptoms & When to Call Your Doctor Also call for palpitations that last longer than 30 seconds, trouble breathing, or coughing up blood.13UNM Health. How Pregnancy Affects the Heart: Normal Symptoms & When to Call Your Doctor These can point to a heart rhythm problem, preeclampsia, or high pressure in the lungs’ blood vessels.14UNM Health. How Pregnancy Affects the Heart: Normal Symptoms & When to Call Your Doctor A fast heartbeat that stays fast, even without other symptoms, should always be looked at by a clinician.15PubMed Central. Tachycardia in pregnancy: when to worry?
Some signs are urgent:
- Chest tightness or pressure in the center of the chest, or pain spreading to the back, neck or arm.16Centers for Disease Control and Prevention. Urgent Maternal Warning Signs and Symptoms
- A fast or pounding heartbeat, or an irregular heartbeat with skipped beats.17Centers for Disease Control and Prevention. Urgent Maternal Warning Signs and Symptoms
- Feeling dizzy, faint or confused.18Centers for Disease Control and Prevention. Urgent Maternal Warning Signs and Symptoms
- Being so short of breath that talking is hard.19Centers for Disease Control and Prevention. Urgent Maternal Warning Signs and Symptoms
Any of these during pregnancy or in the year after birth means calling 911 or going to emergency care, and saying you are or recently were pregnant.
A check-up for a fast pulse usually starts with a repeat pulse and blood pressure reading at rest. Blood tests look at your blood count, iron and thyroid levels. An ECG, a quick painless trace of the heart’s electrical rhythm, is common, and sometimes an ultrasound of the heart rules out a structural problem.
It helps to tell the doctor how fast the pulse was and how you measured it, how long episodes last and what you were doing when they began. Mention any dizziness, breathlessness, chest pain or swelling alongside, plus caffeine, medicines, supplements and recent fluid intake.
Breathlessness and a faster pulse are common in pregnancy, so serious signs can get brushed off. What separates the two is persistence, severity, and symptoms that happen at rest.
Common Causes of a Pulse That Runs Too Fast
A sustained fast heartbeat (a resting heart rate over 100) can be triggered by dehydration, anemia, stress, or heart conditions.20Tampa General Hospital. Heart Rate During Pregnancy In heat, a rapid heartbeat is one sign of dehydration, along with dizziness, headache, dark urine, peeing less, thirst and cramps.21CDC. Clinical Overview of Heat and Pregnancy Dehydration in pregnancy can also bring on early contractions.22CDC. Clinical Overview of Heat and Pregnancy Recheck your pulse once you’ve rested and rehydrated.
Pregnant bodies already carry extra blood volume that has to be kept topped up, so losing fluid through sweat, vomiting or diarrhea can push the pulse up faster than before pregnancy. Morning sickness is an overlooked route into dehydration, since you may be unable to keep fluids down for a day or more. Pale yellow urine is a simple check; dark urine suggests you need more fluids.
Anemia, meaning low iron or too few healthy red blood cells, is common in pregnancy because the body’s oxygen needs rise.23Vinmec Central Park International General Hospital. Overcoming Shortness of Breath and Rapid Heartbeat During Pregnancy The heart beats faster to move enough oxygen, and you may feel breathless, tired and dizzy.24Vinmec Central Park International General Hospital. Overcoming Shortness of Breath and Rapid Heartbeat During Pregnancy In one group of women with iron-deficiency anemia in the second trimester, 9 in 10 had a fast heart rate, and the lower their iron the more likely it was.25PubMed Central. Maternal Myocardial Performance in Second Trimester of Pregnancy With Iron Deficiency Anaemia If your pulse is high and you feel exhausted, ask whether your blood count and iron have been checked.
Only a blood test confirms it, and blood counts are usually checked at routine prenatal visits, so you can ask for your latest result. Treatment is usually iron supplements or iron-rich foods, and the pulse often eases as levels recover. Follow your clinician’s advice on dose rather than starting high doses on your own.
An overactive thyroid causes a faster heartbeat, heat intolerance and tiredness, which overlap with normal pregnancy.26National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Disease & Pregnancy A heartbeat that is both fast and irregular can be one clue to a thyroid problem, though only a blood test confirms it.27National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Disease & Pregnancy Emotional stress, caffeine and certain medicines can contribute to an abnormal heart rhythm.28Tampa General Hospital. Heart Rate During Pregnancy An existing heart condition can worsen under the strain of pregnancy, and high blood pressure conditions like preeclampsia can affect the heart.29Tampa General Hospital. Heart Rate During Pregnancy
Caffeine adds up across a day from coffee, tea, energy drinks and cola. Some cold and decongestant medicines can speed the heart, so ask a pharmacist first. If you suspect a prescribed medicine, check with your doctor before stopping it.
A temporary rise settles within minutes of resting, drinking water or calming down. A pulse still above 100 after 15 to 20 minutes of rest deserves a call. Episodes that keep returning without clear triggers are worth reporting even if brief.
Skipped Beats, Flutters and Palpitations
Palpitations are the feeling of your heart pounding, fluttering or racing. Single extra beats, and patterns where an extra beat comes every second or third beat, are common in pregnancy.30PubMed Central. Clinical approach to palpitations in pregnancy In a heart that is otherwise structurally normal, they need no treatment.31PubMed Central. Clinical approach to palpitations in pregnancy
A harmless skipped beat feels like a brief thud, flip or pause in the chest, often noticed when lying still at night. It usually passes in a second or two without dizziness. Tiredness, caffeine and lack of sleep can make extra beats more frequent, as can stress and dehydration, so changing those is a reasonable first step. Pregnancy can also make you more aware of your heartbeat, so beats that were always there may only now be noticed. A short note of when they happen and what you were doing gives your doctor something useful to work with.
An ECG recorded during an episode shows the type of beat, and with tests showing a structurally normal heart, it can confirm that extra beats are harmless. A portable monitor worn for a day or more can catch episodes that come and go. Normal results usually mean reassurance rather than treatment.
Rarely, a fast heartbeat in late pregnancy or after birth is a sign of a weakening of the heart muscle linked to pregnancy, which doctors call peripartum cardiomyopathy.32PubMed Central. Peripartum Cardiomyopathy: Case Reports It comes with heart-failure symptoms such as breathlessness, rapid breathing and chest pain.33PubMed Central. Peripartum Cardiomyopathy: Case Reports Palpitations with swelling, breathlessness lying flat or chest pain need prompt assessment.
Your Pulse When Lying Down
In the third trimester, lying flat on your back lets the womb press on major blood vessels. The main vein returning blood from your legs and lower body runs alongside your spine, and the weight can squash it. With less blood coming back, the heart has less to pump out. The heart pumps about 16% less blood than when lying on the left side, and flow in the main abdominal artery falls by about a third.34PubMed Central. Preoperative inferior vena cava-abdominal aorta ultrasound examination to guide the positioning of spinal anesthesia to reduce post-spinal hypotension: a prospective, randomized trial That’s why blood pressure can drop and you can feel faint or sick.
Women who feel faint lying this way often show little rise in pulse to make up for it.35Acta Obstetricia et Gynecologica Scandinavica. Hemodynamic changes in women with symptoms of supine hypotensive syndrome So your pulse may not show that lying flat is the problem; if you feel faint, change position rather than rely on the number.
Roll onto your left side and stay there for a few minutes. A pillow tucked behind your back helps you avoid rolling flat during sleep, and getting up slowly from lying or sitting prevents lightheadedness. If faintness doesn’t ease on your side, call your doctor.
Heart Rate and Exercise
US obstetric guidance advises exercise that feels fairly light to somewhat hard.36PubMed Central. Monitoring Physical Activity Intensity During Pregnancy It suggests staying under 60 to 80% of your age-predicted maximum heart rate, usually not above about 140 beats per minute.37PubMed Central. Monitoring Physical Activity Intensity During Pregnancy But because resting pulse rises and maximum pulse falls in pregnancy, heart rate is a less precise guide to effort.38PubMed. Clinical physiology of exercise in pregnancy: a literature review How hard exercise feels is not changed by pregnancy, which makes it a more reliable guide.39PubMed. Clinical physiology of exercise in pregnancy: a literature review Canada, Japan, Spain and the UK pair heart rate with the talk test and an effort scale.40PubMed. Guidelines for exercise during normal pregnancy and gestational diabetes: a review of international recommendations
With the talk test, you should be able to hold a conversation, though not sing. On a 6 to 20 effort scale, aim around 12 to 14, somewhat hard. If you can only gasp a few words, slow down.
A fit person may exceed 140 while still feeling comfortable, and someone newly active may feel strained below it. Use the figure as a loose upper limit and let how you feel set the pace.
Stop for chest pain, dizziness, or a heartbeat that stays racing after you rest. Stop too for breathlessness before starting, contractions, or fluid leaking. Drink water and avoid exercising in heat, which raises the pulse further.
Can You Trust Your Smartwatch
Wearables show promise for tracking activity, sleep and heart measures in pregnancy.41Pharmacia. Wearable health-tracking technologies in pregnancy: capabilities, clinical evidence, and implementation challenges But their accuracy varies and they have limited testing in clinical settings.42Pharmacia. Wearable health-tracking technologies in pregnancy: capabilities, clinical evidence, and implementation challenges Use a watch to spot trends in your resting rate, and confirm worrying readings by counting your pulse by hand.
Most watches estimate pulse by shining light on the skin and detecting blood flow changes, which movement, a loose fit or cold hands can disrupt. Swelling in the wrists and altered blood flow in pregnancy can also affect the sensor. Readings are more dependable at rest than during vigorous exercise.
A single high-heart-rate alert during movement is often just activity. A resting-rate trend that keeps climbing well past the high 70s or 80s is worth mentioning. And never ignore symptoms because the watch reading looks normal.
Your Pulse During Labor and After Birth
In one study of early labor, the average pulse actually dipped during contractions, from about 83 to 74 beats per minute.43Acta Obstetricia et Gynecologica Scandinavica. Maternal heart rate patterns in the first and second stages of labor Every pushing effort raised it, by about 35 beats on average, from roughly 88 to 123.44Acta Obstetricia et Gynecologica Scandinavica. Maternal heart rate patterns in the first and second stages of labor One in 5 women passed 140 beats per minute while pushing.45Acta Obstetricia et Gynecologica Scandinavica. Maternal heart rate patterns in the first and second stages of labor Labor heart rates reach those of moderate to heavy exercise.46PubMed. Maternal heart rate changes during labour A racing pulse while pushing is expected, and your care team is monitoring it.
Resting pulse falls after delivery.47Harvard T.H. Chan School of Public Health. Understanding exercise patterns and heart rate throughout pregnancy By about two weeks after birth it typically settles around 75 beats per minute.48PubMed. Asymptomatic Postpartum Bradycardia: A Case of Spontaneous Resolution in a 34-Year-Old Woman An unusually slow pulse after birth is rare.49PubMed. Asymptomatic Postpartum Bradycardia: A Case of Spontaneous Resolution in a 34-Year-Old Woman The urgent warning signs listed earlier still apply in the year after birth.50Centers for Disease Control and Prevention. Urgent Maternal Warning Signs and Symptoms
In the recovery weeks, blood loss, low iron and poor sleep can keep the pulse higher for a while. Breastfeeding raises fluid needs, so dehydration can still speed the heart. A pulse staying over 100 at rest weeks after birth is worth reporting.