pregnancy and exercise: the effects on heart rate and blood pressure
pregnant individuals are able to recover from exercise in a manner similar to non-pregnant individuals.
3 minute read
close-up of male doctor measuring blood pressure of pregnant woman in clinic
by: craig steinback, graeme purdy, brittany matenchuk, and margie davenport
in the nine short months of pregnancy, cardiovascular and nervous systems have to dramatically adapt to a pregnant individual’s changing body. blood volume increases by 50 per cent, there’s a 30 per cent increase in the amount of blood the heart pumps, and a 20 per cent increase in the resting heart rate.
the autonomic nervous system is responsible for heart rate changes, and simple, non-invasive techniques to measure the system’s health have been developed. baroreflex gain —when the heart rate changes because of blood pressure changes — acts to ensure that blood pressure is maintained during normal activities. changes in the heart rate and the gap between heart beats indicates how active the autonomic nervous system is in checking and adjusting heart rates. both measures can determine health outcomes and how well the heart system functions. we know that pregnancy affects the autonomic control of the heart and that, in people who aren’t pregnant, exercise influences baroreflex gain and changes in heart rate.
the 2019 canadian guideline for physical activity throughout pregnancy
this recent guideline encourages all pregnant individuals without medical issues to exercise for 150 minutes at a moderate intensity, spread throughout three days of the week at the very least. this evidence-based guideline shows that prenatal exercise can reduce, by 40 per cent, the risk of developing gestational diabetes (diabetes caused by pregnancy), gestational hypertension (high blood pressure), and preeclampsia (a complication of high blood pressure), without increasing the risk of having a miscarriage, a small baby, or a baby born before it’s due. although prenatal exercise is established to be both safe and beneficial for both the mother and the fetus, it has been suggested that pregnant people may have an increased risk of having low blood pressure and feeling faint at the end of exercising. the physical reasons for this are not clear.
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this may be because of differences in the autonomic control of the heart and how it responds to changes in blood pressure. the study, therefore, looked at the impact of a single bout of self-induced intense exercise in the first, second, and third trimesters of pregnancy on autonomic function compared to non-pregnant individuals.
what the study found
pregnant individuals had much less of a response to changes in blood pressure (a blunted baroreflex gain) and lower heart rate changes at rest, in part due to their higher resting heart rates, compared to non-pregnant individuals. however, pregnant individuals had similar control of their heart rates during and following exercise compared to non-pregnant individuals.
this suggests that, although autonomic control of the heart changes when pregnant individuals are at rest, these individuals are still able to respond to, and recover from, exercise in a manner similar to non-pregnant individuals. this has important implications for promoting and implementing exercise programs in pregnant individuals because they are at no obvious greater risk of low blood pressure after exercise than their non-pregnant peers.
the bottom line
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pregnant individuals have a lesser heart rate response to changes in blood pressure at rest compared to individuals who are not pregnant. pregnant individuals are able to control their heart rates after exercising in a manner similar to non-pregnant individuals. although low blood pressure after exercising does not appear to be a risk, monitoring the blood pressure of pregnant individuals after exercising should be considered.
craig steinback, graeme purdy, and margie davenport are from the neuromuscular health lab in the program for pregnancy & post partum health at the faculty of kinesiology, sport, and recreation at the university of alberta in edmonton, alberta; and brittany matenchuk is from the department of pediatrics at the university of alberta in edmonton, alberta. this article was based on graeme m. purdy, marina a. james, paige k. wakefield, rachel j. skow, sean van diepen, linda e. may, margie h. davenport and craig d. steinback maternal cardioautonomic responses during and following exercise throughout pregnancy. applied physiology, nutrition and metabolism. published on the web 14 august 2018, doi/10.1139/apnm-2018-0397#.xlidqpnkhm9 .this summary was written for the canadian society for exercise physiology and it has been reviewed by the csep knowledge translation committee.
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pre-screening for physical activity using an evidence-based screening tool is an important first step in ensuring a safe and enjoyable physical activity experience. screening identifies those who many need more evaluation before doing a fitness assessment or becoming more physically active.
please consult csep.ca/pre-screening-for-physical-activity/ for more information.
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