Exercise heart rate limits in pregnancy

What does the evidence say about exercise heart rate during pregnancy?

1. The 140-beats-per-minute ceiling many people still associate with pregnancy exercise traces back to a 1985 guideline and was removed from official guidance in later updates, though providers kept referencing it for years afterward. 1
2. Current guidance points toward keeping heart rate in roughly 60 to 80% of age-predicted maximum alongside a perceived-exertion rating of fairly light to somewhat hard, since a single flat heart rate cap is not a useful restriction given how maximum heart rate naturally declines with age. 1
3. International guidelines vary widely on the exact number: the UK recommends 60 to 90% of maximal heart rate, Japan and Spain use flat caps of 150 and 140 beats per minute respectively, and Norway bases intensity on oxygen uptake rather than heart rate at all, showing there is no single worldwide standard. 2
4. A systematic review of professional exercise recommendations found the consensus approach for healthy pregnant women is moderate intensity judged by a rating of perceived exertion of 12 to 14 on the 6-to-20 Borg scale and or the talk test, with some organizations also citing an age-adjusted heart rate range of 135 to 150 beats per minute for women 20 through 29. 3
5. Resting heart rate itself rises across pregnancy in cohort data, increasing about 6 beats per minute by the first trimester and a further 9 and 15 beats per minute in the second and third trimesters, part of why a single fixed heart rate ceiling does not fit every stage of pregnancy. 4

Is exercise heart rate safe in each trimester?

• First trimester. Resting heart rate is already climbing early on, roughly 6 beats per minute above your very first readings in cohort data, so a workout that feels like your normal effort will read higher on a monitor than it did before pregnancy.
• Second trimester. Heart rate keeps rising as cardiac output increases, which is exactly why guidance has moved away from one flat ceiling like 140 bpm: how the effort feels (the talk test or a perceived-exertion scale) stays the more consistent signal.
• Third trimester. By the third trimester, resting heart rate runs meaningfully higher again, about 15 beats per minute above early pregnancy readings in cohort data, so many current guidelines pair a wider, age-adjusted heart rate range with perceived exertion rather than a single number.