Target Heart Rate During Pregnancy

Pregnancy raises your heart rate on purpose — blood volume, heart rate, stroke volume and cardiac output all increase while vascular resistance falls. For exercise, current U.S. guidance leans on how hard it feels rather than a beats-per-minute ceiling, and the talk test is the everyday version of that. Your age-predicted maximum, below, is context for the percentages that follow — not a target to chase, and never a substitute for your prenatal care team.

The 140 bpm number, and what happened to it

This is the most repeated figure in pregnancy fitness, and its history matters:

• 1985 — ACOG’s first guidance told pregnant women not to exceed 140 bpm during physical activity.
• 1994 and 2002 — the heart rate restriction was removed. The 1994 bulletin was blunt about the reason: there were no human data indicating that pregnant women should limit exercise intensity and lower target heart rates because of potential adverse effects.
• 2015 — ACOG endorsed ratings of perceived exertion instead, noting that heart rate responses in pregnancy are sometimes blunted and sometimes normal, which makes pulse an unreliable gauge. It also introduced the talk test.
• 2020, Committee Opinion 804 — intensity is described as perceived exertion of 12 to 14 on the 6–20 scale and under 60 to 80% of age-predicted maximal maternal heart rate, usually not exceeding 140 beats per minute.

So the number is back in the document, but its job has changed completely. In 1985 it was a ceiling you were told not to cross. In 2020 it is a description of roughly where a moderate effort lands for most people — a consequence of the intensity target, not the target itself. That distinction is what a generation of “stay under 140” advice lost: surveys found clinicians were still repeating the 1985 restriction years after it was withdrawn.

What to use instead

The talk test. The Office on Women’s Health states it in one line: you should be able to talk while exercising, and if not, you may be overdoing it. It needs no device, works in the pool and on a bike, and does not care that pregnancy shifted your resting pulse.

Perceived exertion. Twelve to fourteen on the 6–20 Borg scale is “light” edging into “somewhat hard” — working, breathing noticeably, still conversational.

The weekly dose. At least 2 hours and 30 minutes of moderate-intensity aerobic activity a week, best spread across the week. Those who already did vigorous activity or high volumes before pregnancy can generally keep going, with their provider’s agreement and ongoing review.

Why your resting pulse is higher now

The cardiovascular adaptations of pregnancy are exactly what an athlete’s monitor picks up as “poor recovery”: more circulating blood, a faster resting rate, lower vascular resistance. A resting number that would have been unusual for you a year ago can be normal at 28 weeks. This is also why comparing your pregnancy heart rate data against your pre-pregnancy zones produces alarming, meaningless graphs — the baseline moved.

Stop and call your provider if you have

The Office on Women’s Health lists these as reasons to stop exercising and call as soon as possible: dizziness, headache, chest pain, calf pain or swelling, abdominal pain, blurred vision, fluid leaking from the vagina, vaginal bleeding, less fetal movement, or contractions.

It also flags conditions where a provider will advise against exercise altogether — risk factors for preterm labor, vaginal bleeding, and premature rupture of membranes — plus practical rules: avoid lying on your back after the first trimester, avoid contact sports and activities with a fall risk, do not scuba dive, skip altitudes above 6,000 feet, keep fluids up, and stay out of extreme heat and humidity.

The part no page can replace

Twin pregnancies, pre-existing heart conditions and any high-risk pregnancy change these recommendations entirely. Prenatal care is where your plan gets set, and every clinician quoted above says the same thing: talk to your provider before you start.

This content is informational and does not replace medical evaluation. See the max heart rate calculator for where the age percentages come from, and the child heart rate calculator for what is normal after the baby arrives.