If you are thinking about becoming pregnant you should have already started an exercise regime, or should be starting one now! Due to the many physical and hormonal changes that occur throughout the pregnancy it is not the time to initiate an exercise program.

There are many cardiovascular, respiratory, metabolic, thermoregulatory, and bio mechanical changes that occur throughout the pregnancy. It is important to note that at this time your focus should shift from trying to increase your levels of fitness to maintaining a level of activity that maintains your feeling of well-being.

Why you should continue exercising through your pregnancy?

Studies have proven that active, fit women tend to have fewer complications through their pregnancy
Shorter labour
Less weight gain
Fewer caesarian sections
Fewer spontaneous abortions
Myths about exercising when pregnant

Female reproductive organs are more fragile than males.
False: injuries to reproductive organs occur much less frequently in women than in men as they are well protected within the bony pelvis, in a ligamentous sling, surrounded by musculature. Water-skiing was the only activity that there was a concern about due to the risk of high-velocity water entering the vagina during a fall. Rubber wet-suits being worn by women were recommended.

Newborns are smaller than those of women who did not exercise.
True: birth weight is generally 300-350 g lower but this decreased weight is mainly due to a decrease in subcutaneous fat which has no lasting effect on the baby.

The increase in temperature when exercising that a woman experiences will harm the baby by increasing the baby’s temperature to dangerous levels.
False: the thermoregulatory changes that a woman undergoes when pregnant facilitate heat loss. 15% of heat is lost through the uterine wall and the rest through uteroplacental circulation. Studies have proven that the core temperature of physically fit pregnant women actually decreases when exercising as they are more efficient at core temperature regulation.

Due to blood flow being diverted to working muscles the baby will not receive adequate oxygen or nutrients.
False: while it is true that with moderate exercise overall blood flow to the organs decreases by about 50% it has been proven that the developing foetus receives adequate blood supply due to the
increased cardiac output, which is the amount of blood pumped by the heart in one minute.

The increase in heart rate that a woman experiences when exercising will harm the baby.
True & False: while mild to moderate activity does in fact increase fetal heart rate this does not pose a threat to the baby. Fetal heart rates return to normal levels within 15minutes. During maximal exercise there have been rare cases of foetal bradycardia therefore it is recommended that women who are pregnant do not engage in maximal exercise.

General Guidelines for Exercising when Pregnant from the American College of Obstetricians and Gynecologists

  • Do not begin a vigorous exercise program shortly before or during your pregnancy.
  • Modify your activity and intensity level according to how you are feeling and what symptoms you are experiencing.
  • Keep exercising regularly (3x/week) as opposed to irregularly. You will be better able to gauge your body’s ability and how to modify activities.
  • After the first trimester avoid the supine position (lying on your back) as this position compresses the inferior vena cava, decreasing venous return and cardiac output.
  • Extend your warm-up and cool-down periods
  • Mild to moderate activity, not maximal. Up to 70% maternal aerobic power. Don’t exercise to exhaustion.
  • Monitor intensity level according to how you feel rather than heart rate.

Example of Rating of Perceived Exertion

1 – barely feel it
2 – very light
3 – hard, but could continue
4 – very hard
5 – could not work out any harder
8. Avoid activities that could cause you to lose your balance and fall, or other activities that could cause trauma to the abdominal region
9. Weight bearing activities such as running can be continued into the second and third trimester. Wear good shoes and modify the intensity, duration, and frequency according to how you feel.
10. To ensure proper heat loss especially during the first trimester make sure that you are adequately hydrated, wear appropriate clothing and modify activity according to environmental conditions (heat and humidity).
11. Due to hormonal changes a woman’s ligaments become more lax therefore care should be taken to not go beyond your normal range of motion at any given joint.
12. An active pregnant woman will have to increase her caloric intake by at least 500cal more a day.
13. Post partum activities can be gradually resumed based on physical capabilities.

When exercising while pregnant keep in mind your altered goals – this is not the time to be trying to achieve a new level of fitness or personal records. You should be trying to maintain the sense of mental and physical health and wellness that you have previously achieved by being active

When To Stop Exercising and Conditions That May Make Exercise Risky

If you experience any of the following symptoms stop exercising and call you doctor right away:

  • Bleeding from your vagina
  • Difficult or laboured breathing before you exercise
  • Dizziness
  • Headache
  • Chest pains
  • Muscle weakness
  • Calf pain or swelling
  • Preterm labor
  • Decreased movement of the fetus
  • Leakage of fluid from your vagina
  • Placenta previa

– Foss, M.L., Keteyian, S.J. (1998). Fox’s Physiological Basis for Exercise and Sport. WCB McGraw-Hill: Boston. pp 402-3.
– Kisner, C., Colby, L.A. (2002). Therapeutic exercise Foundations and Techniques. F.A. Davis Company: Philadelphia. pp 681-705.
– American Council on Exercise. (1996). Personal Trainer Manual. ACE: San Diego. pp 345-6.

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