Exercise in Pregnancy

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Additional reading for today in ACOG Committee Opinion 804!

What are the definitions of physical activity and exercise? 

  • Per ACOG: 

    • Physical activity: bodily movement produced by contractions of skeletal muscles in all stages of life

    • Exercise: physical activity consisting of planned, structured, and repetitive bodily movements done to improve one or more components of physical fitness 

    • Physical activity can maintain and improve cardiorespiratory fitness, reduce the risk of obesity and associated comorbidities, and results in greater longevity 

Is exercise safe in pregnancy?

  • Yes!

    •  Not just in pregnancy, but for all individuals, the US Department of Health and Human Services Physical Activity Guidelines for Americans says: 

      • At least 150 min of mod intensity aerobic activity per week

      • Recommended also in pregnancy and postpartum period 

      • Those that engaged in vigorous-intensity aerobic activity or who were physically active before pregnancy can continue those activities 

      • Few maternal conditions that would not allow aerobic exercise 

  • What are the downsides of not exercising?

    • Physical inactivity is the 4th leading risk factor for early mortality worldwide 

    • Physical inactivity and weight gain in pregnancy have been recognized as independent risk factors for maternal obesity and pregnancy related complications like GDM  

  • What are the benefits of exercising? 

    • Increased likelihood of vaginal delivery! 

    • Low incidence of: excessive weight gain, GDM, gestational hypertensive disorders, preterm birth, c-section, lower birth weight 

  • What exercises are safe? 

    • Aerobic: walking, stationary bike, aerobic exercises, dancing, stretching, water aerobics 

    • Anaerobic: resistance training (weights, elastic bands) 

    • Borg rating of perceived exertion: 6 - 20 (6 to 7 is very, very light, and 19-20 is very, very hard) 

      • Recommend moderate intensity, which is about a 13-14 (somewhat hard) 

        • About 20-30 min per day for most days of the week 

      • Also talk test: if you can talk while exerting yourself, likely not over exerting 

Note: ACOG issued a correction to this table; it should read “First Trimester, Less Than 12 Weeks Gestation.”

What are some modifications we should consider in pregnancy? 

  • Changes in pregnancy 

    • Weight gain, difference in weight distribution 

      • About 60% of pregnant patients will experience low back pain 

    • Increase in blood volume, heart rate, stroke volume, cardiac output = normal (recall our very first few episodes on physiologic changes in preg!)

      • Maintaining supine positioning after 20 weeks may lead to decrease venous return → can lead to SOB, dizziness, hypotension, etc 

    • Minute ventilation increases by 50% 

  • Other modifications: 

    • Remember to stay well hydrated, wear loose-fitting clothing, and avoid high heat and humidity (ie. hot yoga) 

    • Exercise by itself isn’t expected to increase body temp to point of concern 

  • Fetal response 

    • Studies show some minimal to mod increase in fetal heart rate by 10-30 bpm during maternal exercise 

    • Three meta-analyses show that there is minimal to no difference in birth weight 

    • However, women who continue to exercise vigorously in third trimester are more likely to deliver babies weighing 200-400g less than controls, though no increased risk of FGR 

When to stop exercising 

  • Don’t exercise if:

    • Have vaginal bleeding, abdominal pain, regular painful contractions, leaking fluid 

    • Dyspnea before exertion, dizziness, headache, chest pain

    • Muscle weakness affecting balance, calf pain or swelling  

Special considerations 

  • Obesity

    • Encourage patients to have healthy lifestyle modification in pregnancy that include physical activities and judicious diets 

    • Can start with low-intensity, short periods of exercise if not exercising already 

    • Then can build up gradually 

  • Athletes

    • Vigorous-intensity exercise even in 3rd trimester appears to be safe and healthy for most pregnancies 

    • Further research is needed for exercise intensity exceeding 90% of max heart rate