Exercise during pregnancy: what the science actually shows

For decades, pregnancy was treated as a state of fragility requiring movement restriction. Dr. Margie Davenport, exercise physiologist and professor at the University of Alberta, has led the research that overturned that paradigm. The 2019 Canadian guidelines, which she co-developed, conclusively demonstrated that exercise during pregnancy is not only safe but significantly reduces the risk of complications for both mother and baby.

What the evidence actually shows: concrete risk reductions

The 2019 guidelines reviewed hundreds of randomized controlled trials and found that moderate-intensity exercise during pregnancy produces:

• 40% reduction in the risk of developing preeclampsia (high blood pressure with end-organ damage)
• 40% reduction in the risk of gestational diabetes
• 67% reduction in the odds of developing depression during pregnancy
• 45% reduction in the odds of developing depression in the postpartum period
• 50% reduction in the risk of pregnancy complications in women who remain active until delivery vs. those who reduce activity in the first or second trimester
• No increased risk of preterm birth, small baby, or miscarriage in women who exercise compared to those who do not

These numbers come from randomized controlled trials — the highest level of available evidence, not observational data.

The recommendation: 150 minutes per week as a floor

The 2019 Canadian guideline, adopted almost identically by the World Health Organization in 2020, recommends at least 150 minutes of moderate-intensity physical activity spread over three or more days per week, including aerobic exercise, resistance training, and pelvic floor muscle training.

Even activity levels well below that minimum produce significant benefits:

• 10 minutes of brisk walking per day reduces the odds of developing preeclampsia by 25%
• 15 minutes per day reduces the risk of gestational hypertension or excessive weight gain by 25%

Moderate intensity means a pace at which the heart rate rises and there is light sweating, but you can still hold a conversation.

The 140 beats-per-minute myth

This restriction appeared in a 1985 guideline and was designed as a placeholder. Forty years later it still circulates and causes confusion. There is no evidence that exceeding 140 beats per minute is harmful. Resting heart rate during pregnancy rises approximately 15 beats per minute, which already makes standard heart rate zones difficult to interpret. Perceived exertion and the ability to talk are more reliable intensity markers.

No other guideline worldwide sets this 140 bpm limit. It was reintroduced in a table in the ACOG guideline, continuing to generate clinical confusion despite lacking support in current evidence.

High-intensity exercise and resistance training

Research published after the 2019 guidelines has begun examining higher intensities:

High-intensity interval training (HIIT): Studies using 10 one-minute intervals at 90% of maximal effort showed that both mother and baby tolerated the load well. Fetal blood flow and fetal heart rate remained within normal ranges even at intensities previously considered off-limits.

Resistance training: A survey of nearly 700 women who were lifting more than 80% of their 1RM before pregnancy and continued during gestation found a 51% reduction in the risk of complications compared to those who followed guidelines and stopped. Studies are currently underway examining the fetal safety of heavy back squats, bench press, and deadlifts during pregnancy.

Pelvic floor training deserves dedicated attention

The 2019 guideline includes a specific recommendation for pelvic floor muscle training during pregnancy. Randomized controlled trials show a 35–37% reduction in the risk of urinary incontinence in women who practice it regularly.

Postpartum exercise: earlier rather than later

The belief that you must wait six weeks before resuming exercise has no strong evidence base. The 2025 Canadian postpartum guidelines conclude that resuming or beginning activity within the first 12 weeks improves mental health, reduces the risk of postpartum depression, and produces better sleep quality — though not necessarily longer duration.

Research also shows that women who maintained their fitness during pregnancy have a reduced risk of injury in the postpartum period, likely because they preserved the strength, motor skills, and proprioception specific to their activity.

Absolute and relative contraindications

Exercise is recommended in the absence of contraindications. Absolute contraindications include conditions such as placental abruption. Relative contraindications, such as gestational hypertension or twin pregnancy, require a conversation with the healthcare provider, but in most cases exercise continues to be beneficial with appropriate modifications.

The one activity clearly contraindicated during pregnancy regardless of fitness level is scuba diving, due to the risk of nitrogen buildup in the still-developing fetal lung.