The medical instruction that pregnant women should rest and avoid strenuous activity was based on theoretical concerns rather than evidence, and has been comprehensively revised by the research of the past two decades. The current RCOG, NHS, and NICE guidance recommends that women with uncomplicated pregnancies aim for at least 150 minutes of moderate-intensity physical activity per week throughout pregnancy. This is not a minimum to be cautiously approached but a target associated with meaningful benefits for maternal and fetal outcomes.
Benefits for the Mother
The benefits of regular exercise during pregnancy for maternal outcomes are well-documented and clinically significant. A systematic review and meta-analysis by Bø et al. in the British Journal of Sports Medicine found that exercise during pregnancy significantly reduced the risk of gestational diabetes by 38 percent, gestational hypertension and preeclampsia, excessive gestational weight gain, caesarean section rates, and postnatal depression. Women who exercised throughout pregnancy also reported better sleep quality, less back pain, better mood, and greater energy during what is frequently a physically demanding period.
Benefits for the Baby
Exercise during pregnancy does not compromise fetal development in low-risk pregnancies and appears to confer direct benefits to the offspring. Studies have found that infants born to mothers who exercised throughout pregnancy have more favourable body composition, lower rates of macrosomia, and in some studies, better neurodevelopmental outcomes. During moderate-intensity exercise, fetal heart rate increases appropriately and returns to baseline promptly after exercise ceases, reflecting normal cardiovascular adaptation. The fetal oxygen supply is maintained during moderate exercise, as the combination of increased cardiac output and preferential uteroplacental blood flow compensates for the diversion of blood to exercising muscle.
What Is Safe and What to Avoid
Most forms of exercise that a woman was performing before pregnancy can be continued in modified form during it. Walking, swimming, cycling on a stationary bike, yoga, Pilates, and resistance training with appropriate modifications are all considered safe throughout uncomplicated pregnancy. Running can continue if it was part of the pre-pregnancy routine, with intensity reduced as pregnancy progresses and symptoms indicate. High-impact contact sports, activities with significant fall risk including horse riding and skiing, scuba diving, and any activity requiring lying flat on the back for prolonged periods after the first trimester should be avoided. The body contact supine lying restriction applies because the gravid uterus can compress the inferior vena cava, reducing venous return and causing maternal and fetal hypotension.
The Talk Test and Perceived Exertion
Heart rate targets for exercise intensity used in non-pregnant adults are not reliable during pregnancy due to physiological changes in resting heart rate and cardiac output. The talk test is a practical alternative: exercise should be moderate enough to maintain a conversation but not so light that conversation requires no effort. This corresponds to approximately 50 to 70 percent of maximum heart rate for most women and is safe for both maternal and fetal cardiovascular parameters throughout uncomplicated pregnancy.
- Aim for 150 minutes of moderate-intensity exercise per week throughout pregnancy, in sessions of at least 20 minutes each
- Continue pre-pregnancy exercise types with appropriate modification: reduce impact and intensity as pregnancy progresses
- Swimming and water-based exercise are particularly well-suited to pregnancy: the water supports the weight of the uterus and reduces musculoskeletal strain
- Stop and seek medical advice if you experience vaginal bleeding, dizziness, severe shortness of breath, chest pain, painful uterine contractions, or fluid leaking from the vagina during exercise
- Avoid exercise in hot and humid conditions: pregnancy impairs thermoregulation, increasing overheating risk
Sources
- Bø, K., et al. (2016). Exercise and pregnancy in recreational and elite athletes: evidence summary from the IOC expert group meeting. British Journal of Sports Medicine, 50(10), 571-589.
- RCOG. (2006, updated 2019). Exercise in pregnancy. Royal College of Obstetricians and Gynaecologists Statement No. 4.
- Mottola, M.F., et al. (2018). 2019 Canadian guideline for physical activity throughout pregnancy. British Journal of Sports Medicine, 52(21), 1339-1346.