SUMMARY:  

• ACOG has updated their Committee Opinion on exercise and physical activity during pregnancy and postpartum. Not only is lack of exercise a leading mortality risk factor, physical activity is crucial during pregnancy due to its association with risk reduction for gestational diabetes, cesarean section, operative vaginal delivery. Exercise also convey benefits in the postpartum period, reducing recovery time postpartum and preventing postpartum depression. Although modification may be necessary due to physiology of pregnancy, exercise is a key part of a healthy pregnancy and should be encouraged. No studies show bedrest improves outcomes in women at risk for preterm birth and multiple studies document negative effects of activity restriction.  

Low-Risk Pregnancies 

• Perform a thorough clinical exam prior to initiation of exercise program to ensure no medical contraindications 
• Activity restriction should not be prescribed to prevent preterm birth 
• Similar to all Americans, recommendation is for 150 minutes of moderate intensity aerobic activity per week during pregnancy and postpartum 
• Safe and beneficial activities include 
  • Walking | Stationary cycling | Aerobic exercises | Dancing | Resistance exercises (weight, elastic bands) | Stretching | Hydrotherapy/water aerobics  

Implementing and Recommending an Exercise Program 

• Motivation counseling can be borrowed from smoking cessation tools such as “the Five A’s”: Ask, Advise, Assess, Assist, and Arrange 
• Set goal of 20 to 30 minutes daily on most days of the week 
• Best gauge of “moderate intensity” exercises 
  • Rely on perceived exertion: “Somewhat hard” (13 to 14 on Borg ratings scale out of 20) rather than heart rate response 
• “Talk Test”  
  • If you can carry on a conversation, typically this level of activity would not be associated with over-exertion 
• Consider the pool 
  • Aquatic exercise during pregnancy (three 60-minute exercises) may lead to greater rate of intact perineum after childbirth  

Benefits of Physical Activity & Exercise 

• Higher incidence of vaginal delivery 
• Lower incidence of the following  
  • Excessive weight gain | GDM | Hypertensive disorders | Preterm birth | Cesarean birth | LBW  
• Physical activity in low risk pregnancies is not linked to the following  
  • Miscarriage | Poor fetal growth MSK injury | Preterm delivery  
• Risks of physical inactivity and excessive weight gain are independent risk factors for the following  
  • Maternal obesity 
  • Pregnancy complications including GDM 

Anatomic and General Considerations 

• Progressive lordosis during pregnancy leads to increased force on the joints and spine   
  • Related back pain occurs in 60% of pregnancies  
  • Abdominal and back muscle strengthening reduces risk 
• Position modifications 
  • Supine position >20 weeks may lead to decreased venous return and hypotension 
  • Position modifications for supine activities should be considered  
• Counsel patients regarding the benefits of  
  • Hydration 
  • Loose-fitting clothing 
  • Avoidance of high heat and humidity (especially during the first trimester) | While there is concern regarding exposure to high heat sources and NTDs (hot tubs, saunas, fevers) a recent study did not find a relationship between exercise and NTDs (see ‘Related ObG Topics’)  

KEY POINTS:

Physiologic Considerations 

Cardiac Changes

• Blood volume increases 
• Stroke volume increases
• Systemic vascular resistance decreases
• Cardiac output increases  
  • First trimester: 5% to 10%  
  • Second and third trimester: 35% to 45%  
  • During labor: 50% (second stage) and 60% to 80% in the first hour postpartum (with rapid return to normal) 
• Heart rate increases 
  • Third trimester: 15% to 20%  
  • Contractions during labor: 40% to 50%  
• Blood pressure 
  • First and second trimesters: Declines due to decreased systemic vascular resistance  
  • Third trimester: 5% increase 
  • During labor (with contractions): SBP increases 15% to 25% | DBP 10% to 15%  
  • Postpartum: Increases 5% to 10% | May increase again 3 to 6 days postpartum due to fluid shifts 
• Blood or plasma volume  
  • Second trimester: 50% increase 
  • During labor: 500cc increase
  • 3 to 6 months postpartum: Returns to prepregnancy levels  

Respiratory Changes 

• Minute ventilation increases 50% due to increased tidal volume 
• Decrease in pulmonary reserve leads to less oxygen availability and slight impairment of anaerobic exercise 
• Physiologic respiratory alkalosis of pregnancy may not fully compensate for metabolic acidosis of strenuous exercise, particularly in overweight or obese patients 
• Aerobic exercise in pregnancy
  • Should not be avoided 
  • Can improve aerobic capacity in normal and overweight patients 

Warning Signs and Considerations 

• Signs to discontinue an exercise program include 
  • Vaginal bleeding | Abdominal pain | Regular contractions | Amniotic fluid leakage | Dyspnea before exertion \ Dizziness | Headaches | Chest pain | Muscle weakness affecting balance | Calf pain/swelling 
• Prolonged intense exercise  
  • “Women who were regular exercisers before pregnancy and who have uncomplicated, healthy pregnancies should be able to engage in high-intensity exercise programs, such as jogging and aerobics, with no adverse effects” 
  • >45 minutes can lead to hypoglycemia | Encourage adequate calorie intake or limiting length of exercise  
• Elite athletes  
  • Defined as several years’ experience in a particular sport | Usually train 2 per day, at least 5 days a week 
  • Literature on safety is limited | Concern regarding injury and impact of Valsalva on FHR  
  • “Prudent’ to  
    • Obtain medical approval | Decrease resistance load | Avoid high-impact activities with risk of blunt trauma  

Occupational Physical Activity  

• Evidence regarding poor fetal-maternal health outcomes based on occupational physical activity is mixed  
  • Some studies have demonstrated small to no risk while other studies report a dose-response relationship between total daily burden lifted and preterm birth, with lifting >20 kgs more than 10 times/day highest risk 
• The National Institute for Occupational Safety and Health (NIOSH) provides an algorithm to determine maximum recommended weight limit for lifting acceptable to 90% of healthy women  

Click Here to See NIOSH Provisional Recommended Weight Limits for Lifting at Work During Pregnancy

Postpartum Exercise 

• Exercise tends to decrease after childbirth leading to weight gain and obesity postpartum 
• Pelvic floor exercises can be initiated in the immediate postpartum period 
• Abdominal strengthening exercises (crunches or “drawing-in exercise” – maneuver to increase abdominal pressure by pulling in abdominal wall muscles) can decrease diastasis recti abdominus 
• Lactation 
  • Exercise postpartum does not affect lactation  
  • Consider breastfeeding or expressing milk prior to exercise to avoid engorged breast discomfort  
  • Encourage adequate hydration  

Learn More – Primary Sources:  

ACOG Committee Opinion 804:  Physical Activity and Exercise During Pregnancy and Postpartum 

CDC/NIOSH: Reproductive Health and The Workplace

Related ObG Topics:

SMFM: Guidance on Reduced Activity and Bed Rest for Pregnancy Complications

The Physical Activity Guidelines for Americans – HHS Recommendations

Is Maternal Core Temperature Elevated Beyond a Critical Threshold During Exercise in Pregnancy?

Does Exercise Alter Blood Flow to the Uterus During Pregnancy?

Does Exercise During Pregnancy Impact Hypertension or Macrosomia?

Does Exercise During Pregnancy Improve Infant Neuromotor Development?