Exercise in Pregnancy

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 

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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% 

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• 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