Many pregnant women have a desire to start or continue healthy fitness habits during their pregnancies, but they do not know where to turn to get advice on what is considered “safe” for the mother and baby. Below, we will outline recent evidence-based research articles that detail the effects that exercise and fitness can have on pregnancy symptoms, body mass, fitness for the mother, as well as the short and long-term effect on the child, both in utero and postpartum.

Maternal Fitness and Pain Tolerance

While we understand that “fitness” includes multiple parameters, for the purposes of this blog, we will focus on aerobic endurance and body composition.

  • Aerobic Endurance: During the 5th week of gestation, alterations to the cardiovascular system occur to supply the fetus with increased blood and oxygen supply, while simultaneous remodeling of the maternal thoracic cage changes, each of which can reduce lung volumes and increase the difficulty of breathing (1). This can be combatted by participating in aerobic exercise as pregnancy symptoms permit, and can actually improve aerobic fitness past the woman’s pre-pregnancy baseline.
  • Body Composition: Pregnancy causes physiological, endocrine, and metabolic changes that increase the prevalence of insulin resistance, which can increase weight gain in women (2). Women who exercise at least three times per week for the duration of their pregnancy have been reported to have a lower chance of gaining excessive gestational weight (3).
  • Pain Tolerance: It has been suggested that women who participate in moderate to high impact activities (jogging, etc) have a decreased risk of pelvic girdle pain(4), and women that adopt a stability ball program for core stability have less low back pain that interferes with daily activities throughout the pregnancy (5).

Risk of Miscarriage

Light to moderate exercise activity does not increase the risk of miscarriage, and may, in fact, decrease the risk of miscarriage(6) and preterm delivery (7,8) in otherwise healthy women who participate in supervised exercise programs. If the mother has a prior history of an eating disorder, exercise can cause symptoms that may increase the risk of a miscarriage or intrauterine growth restriction1.

Fetal Health

While the fetus’s neurological system is in the early stages of development, raising the core body temperature of 103 degrees F or above is contraindicated, as it can increase the risk of defect. With this in mind, however, Bo et al (2016) found that exercising in a controlled environment (indoors at a moderate intensity) is very unlikely to raise temperatures to an unhealthy level, however strenuous, prolonged exercise in hot or humid weather can be dangerous.

Postpartum Infant Health

Blaize et al (2015) found that when a mother exercises during pregnancy, an infant has a higher likelihood of being at less risk for metabolic abnormalities, cancer, and have improved cardiovascular health. Similarly, infants of mothers who participated in exercise during pregnancy have a higher heart rate variability during infancy, which may suggest an improvement in their autonomic programming10.

Conclusion

Exercise during pregnancy has many benefits to both mother and baby, however, some risks may be associated if the mother has a prior history of conditions contraindicated to exercise activity. As with starting any exercise program, it is important to consult with your healthcare practitioner of choice, and even more important to be guided through exercise programming by someone specializing in pregnancy-related exercise.

The Department of Health and Human Sciences8 released recommendations on maternal exercise during pregnancy in a 2015 article, as follows:

  • Low-risk pregnant women
    • Frequency: at least 3 times per week
    • Intensity: mild to moderate (30-70% HRR)
    • Duration: at least 25 minutes at mild to moderate, no more than 40 minutes at higher intensities
    • Type: walking/aerobic activity, body-weight supported activity
  • Women at risk for Gestational Diabetes Mellitus
    • Frequency: at least 3 times per week
    • Intensity: mild to moderate (30-70% HRR)
    • Duration: 35-40 minute sessions at mild intensity, or at least 25 minutes at moderate intensity
    • Type: walking/aerobic activity; body-weight supported activity
  • Women diagnosed with Gestational Diabetes Mellitus
    • Frequency: at least 3 times per week, preferably following a meal
    • Intensity: 30% HRR, increasing to at least 60%HRR
    • Duration: 25 minutes per session to begin, increasing to at least 40 minutes per session
    • Type: walking/aerobic activity; body-weight supported activity

If you have additional questions regarding exercise and pregnancy, please reach out to one of the skilled clinicians at Set PT, or to your OB/GYN!

References:
  1. Bø, K., Artal, R., Barakat, R., Brown, W., Davies, G. A., Dooley, M., … & Kinnunen, T. I. (2016). Exercise and pregnancy in recreational and elite athletes: 2016 evidence summary from the IOC expert group meeting, Lausanne. Part 1—exercise in women planning pregnancy and those who are pregnant. British journal of sports medicine, 50(10), 571-589.
  2. Mottola, M. F., & Artal, R. (2016). Fetal and maternal metabolic responses to exercise during pregnancy. Early human development, 94, 33-41.
  3. Harris, S. T., Liu, J., Wilcox, S., Moran, R., & Gallagher, A. (2015). Exercise during pregnancy and its association with gestational weight gain. Maternal and child health journal, 19(3), 528-537.
  4. Owe, K. M., Bjelland, E. K., Stuge, B., Orsini, N., Eberhard-Gran, M., & Vangen, S. (2015). Exercise level before pregnancy and engaging in high-impact sports reduce the risk of pelvic girdle pain: a population-based cohort study of 39 184 women. British journal of sports medicine, bjsports-2015.
  5. Yan, C. F., Hung, Y. C., Gau, M. L., & Lin, K. C. (2014). Effects of a stability ball exercise programme on low back pain and daily life interference during pregnancy. Midwifery, 30(4), 412-419.
  6. Schlüssel MM, Souza EB, Reichenheim ME, et al. Physical activity during pregnancy and maternal-child health outcomes: a systematic literature review. Cad Saude Publica 2008;24(Suppl 4):s531–44.
  7. Barakat, R., Pelaez, M., Montejo, R., Refoyo, I., & Coteron, J. (2014). Exercise throughout pregnancy does not cause preterm delivery: a randomized, controlled trial. Journal of physical activity & health, 11(5).
  8. Guendelman, S., Pearl, M., Kosa, J. L., Graham, S., Abrams, B., & Kharrazi, M. (2013). Association between preterm delivery and pre-pregnancy body mass (BMI), exercise and sleep during pregnancy among working women in Southern California. Maternal and child health journal, 17(4), 723-731.
  9. Blaize, A. N., Pearson, K. J., & Newcomer, S. C. (2015). Impact of maternal exercise during pregnancy on offspring chronic disease susceptibility.Exercise and sport sciences reviews, 43(4), 198-203.
  10. May, L. E., Scholtz, S. A., Suminski, R., & Gustafson, K. M. (2014). Aerobic exercise during pregnancy influences infant heart rate variability at one month of age. Early human development, 90(1), 33-38.