This information is adapted from “A Modern Approach to Exercise During Pregnancy” a continuing education course authored by Danielle Spangler and produced by Fitness Learning Systems.
Historically, prenatal physical activity has been influenced by necessity, race, ethnicity, social status, wealth, and culture. In the 18th century royal mothers-in-waiting may have been confined to bed while their equally pregnant servants catered to their needs. Peasant women were expected to work alongside their husbands, bear their children in the fields, and return immediately to their labors while the high-born women were lavished with care in late 19th century, early 20th century China.
As recently as the twentieth century, there were varying philosophies regarding the appropriate level of physical activity for prenatal women. In the 1920s and 1930s, a program of prenatal exercise was introduced in the United States with the goal of improving prenatal fitness to facilitate delivery, aid in return to pre-pregnancy weight, reducing labor pain, and improved fetal oxygenation. (Symons Downs 2012)
However, by 1949, the standard level of physical activity recommended for prenatal women consisted of housework, gardening, occasional swims, and short daily walks totaling one mile. Sports were to be avoided. (Symons Downs 2012)
In 1985, the American College of Gynecologists and Obstetricians (ACOG) issued its first recommendations for prenatal physical activity that endorsed aerobic exercise but cautioned care when engaging in high impact activities. Limits on duration were advised at no more than 15 minutes of strenuous activity, a heart rate of no greater than 140 beats per minute, and a core body temperature of no more than 100.4°F. These very conservative guidelines were developed by a panel of obstetricians, evidently without the input of pre and postnatal women. (Symons Downs 2012).
ACOG has since modified the pre and postnatal exercise recommendations. As of 1994 ACOG has changed their strict stance on maintaining a heart rate range below 140 bpm to accepting the rate of perceived exertion from mild-moderate, and a heart rate guideline of 50 -60% of maximum heart rate (HRmax).
ACOG maintains its stance to avoid exercises where there is a risk of falling or abdominal trauma and recommends 30 minutes or more of daily moderate exercise when no obstetric complications are present.
Pregnancies are considered high risk if one or more of the following factors are present:
- The mother is age 35 or over
- The pregnancy is a multiple gestation (more than one baby)
- The mother has a history of miscarriages
- If the mother has diabetes
- If the mother has thyroid disorders
- If the mother has anemia
- The mother is obese
- The mother has a sedentary lifestyle
Relative contraindications to aerobic exercise during pregnancy should be evaluated between the woman, her obstetrician, and her qualified fitness trainer. (ACSM 2018)
These conditions include:
- Severe anemia
- Unevaluated maternal cardiac arrhythmia
- Chronic bronchitis
- Poorly controlled type 1 diabetes
- Extreme morbid obesity
- Extreme underweight (BMI<12)
- History of extremely sedentary lifestyle
- Intrauterine growth restriction in current pregnancy
- Poorly controlled hypertension
- Orthopedic limitations
- Poorly controlled seizure disorder
- Poorly controlled hyperthyroidism
- Heavy smoker
Aerobic exercise during pregnancy is absolutely contraindicated for women who experience the following conditions: (ACSM 2018)
- Hemodynamically significant heart disease- heart disease that restricts blood flow
- Restrictive lung disease
- Persistent second or third trimester bleeding
- Incompetent cervix or cervical insufficiency – pressure from baby on a weak cervix causes the cervix to open before the baby should be born
- Premature labor in current pregnancy
- Multiple gestation at risk for premature labor
- Preeclampsia- high blood pressure with signs of damage to other organs (live, kidneys)
- Pregnancy-induced hypertension
- Ruptured membranes- amniotic sac membranes are ruptured
- Placenta previa- placenta low in uterus and covering the cervix.
When working with a pregnant client, it is important to understand the difference in acute exercise responses (what happens during exercise) as compared to a nonpregnant client. Understanding these changes will also help you better understand what is happening in a current nonpregnant client’s body after they become pregnant allowing you to look for, monitor, and expect these changes as a normal part of the body’s reaction. Understanding physiological responses during pregnancy allows you to help your client exercise safely and effectively, and alerts you to any possible complications. Because of the changes that accompany pregnancy, it is not recommended that you use submaximal exercise protocols to predict maximal aerobic capacity in exercise testing as the results will not be accurate. Physiological responses should be used simply to monitor your client and help them understand why and how to make adjustments in exercise intensity and duration if needed when pregnant.
For more information about acute exercise responses during pregnancy, see “A Modern Approach to Exercise During Pregnancy.”
Bibliography:
- Downs, Danielle & Chasan-Taber, Lisa (2012) Physical activity & pregnancy. past & present evidence & future recommendations. Research Quarterly for Exercise and Sport. Dec. 83, 485-502.
- American College of Obstetricians and Gynecologists. (1994). ACOG Technical Bulletin, Washington, DC: No.189.
- American College of Obstetricians and Gynecologists. (2002). ACOG Committee Opinion. Washington, DC: No.267
- American College of Obstetricians and Gynecologists. (2015). Physical Activity and Exercise During Pregnancy and the Postpartum Period. ACOG Committee Opinion. Washington, DC: No.650
- American College of Sports Medicine (ACSM) (2018) ACSM’s Guidelines for Exercise Testing and Prescription. 10th edition. Wolters, Kluwer publisher.
- Spangler D. (2019) A Modern Approach to Exercise During Pregnancy. www.Fitness Learning Systems.com
