Resting heart rate starts rising early in pregnancy, often within the first few weeks, and climbs steadily until it peaks in the late second to early third trimester. The total increase is typically 10 to 20 beats per minute above your pre-pregnancy baseline, representing a 20% to 25% jump. If your pre-pregnancy resting heart rate sat around 65 BPM, you can expect it to reach the mid-70s to mid-80s at its highest point.
How Heart Rate Changes Week by Week
The rise isn’t sudden. It’s a gradual, steady climb that begins in the first trimester and continues through most of pregnancy. A large review of over 36,000 pregnancies found the average heart rate at 10 weeks was 79.3 BPM, climbing to 86.9 BPM by 40 weeks. That’s roughly a 10% increase overall, though individual variation is wide.
Data from the Apple Women’s Health Study at Harvard found a median pre-pregnancy resting heart rate of 65.5 BPM, peaking at 77 BPM around 8 weeks before delivery (roughly 32 weeks of gestation). After that peak, the heart rate may hold steady or slightly decline as you approach your due date. This pattern makes the late second trimester through early third trimester the period when you’ll likely notice the biggest difference from your usual baseline.
Why Your Heart Works Harder During Pregnancy
Your body undergoes massive cardiovascular changes to support a growing pregnancy. Total blood volume increases by about 45% above pre-pregnancy levels, though the range can be anywhere from 20% to 100%. Plasma (the liquid portion of blood) increases proportionally more than red blood cells, which is why mild anemia is common and considered normal during pregnancy.
All that extra blood needs to be pumped somewhere, and your heart adapts in two phases. Early in pregnancy, it increases the amount of blood pushed out with each beat (stroke volume). By the end of the second trimester, stroke volume plateaus or starts to fall. At that point, your heart compensates by beating faster instead. This is why heart rate becomes especially noticeable in the third trimester. By 24 weeks, your heart may be pumping up to 45% more blood per minute than it did before pregnancy.
Hormonal shifts play a role too. A recent study tracking wearable sensor data from 99 pregnancies found a remarkably strong correlation between resting heart rate fluctuations and pregnancy hormone levels, suggesting that hormones like progesterone and estrogen are directly driving many of these cardiovascular changes by relaxing blood vessel walls and lowering resistance.
What’s Normal and What’s Not
There is no officially defined upper limit for heart rate in pregnancy, which can make it tricky to know when a higher reading is worth worrying about. A resting heart rate consistently above 100 BPM was traditionally considered the threshold for concern, but experts now recognize this cutoff flags too many healthy pregnancies unnecessarily. At the same time, waiting until 120 BPM risks missing real problems. The honest answer is that no single number works for every pregnant person.
What matters more than the number itself is the pattern and any accompanying symptoms. A persistent resting tachycardia (a heart rate that stays elevated rather than spiking briefly with activity or stress) is considered a red flag by the UK’s MBRRACE maternal safety report, especially when paired with breathlessness or chest pain. Brief episodes of a racing heart that resolve on their own are common and usually harmless. A heart rate that stays high at rest and comes with lightheadedness, chest tightness, or difficulty breathing is a different story.
Tracking Your Heart Rate at Home
Consumer wearables like Apple Watch, Fitbit, and Garmin devices are increasingly used to monitor resting heart rate during pregnancy, and the data suggests they do a reasonable job. Research published in The Lancet’s eBioMedicine found that wearable sensor data closely tracked expected hormonal and physiological changes throughout pregnancy. These devices can help you spot trends over weeks and months, which is more useful than any single reading.
One caveat: wearable measurements can be influenced by weight and BMI changes during pregnancy, and the data on how much this affects accuracy is still incomplete. Use your device to watch for gradual trends rather than reacting to any one reading. A slow, steady rise of 10 to 20 BPM over the course of your pregnancy is exactly what the research predicts. A sudden, sustained jump that doesn’t match the expected pattern is worth mentioning to your provider.
After Delivery
Your cardiovascular system doesn’t snap back to its pre-pregnancy state immediately after birth. The same changes that took months to develop take time to reverse. Most of the major cardiac adaptations, including the elevated heart rate, begin unwinding in the first few weeks postpartum, but full recovery to your pre-pregnancy baseline can take several months. If you’re tracking with a wearable, expect a noticeable drop in resting heart rate in the first weeks after delivery, with a slower return to your original numbers over the following months.