10 May 2017
Dr Brandi Cole
Gone are the days when pregnancy was considered a time for confinement, a 9-month sentence to the couch, to lie there and “rest” as your baby developed, while overindulging on any food that took your fancy because you were “eating for two”. It is now generally accepted by society that healthy pregnant women who participated in physical activity prior to pregnancy, and are experiencing an uncomplicated pregnancy, can and should continue to exercise throughout pregnancy until birth or until such times that it becomes too uncomfortable to do so. What is less well known, however, and sometimes feared, is that women who were inactive prior to pregnancy, should be encouraged to become physically active during pregnancy, even if it is for the first time ever in their lives, albeit by starting with low intensity activities and consulting their health care provider prior to initiating exercise.
In a world where physical inactivity is the fourth leading risk factor for global mortality behind tobacco smoking, high blood pressure and elevated blood glucose, the suggestion that a pregnant woman should be physically active is sometimes met with apprehension. Pregnancy is an ideal time for behavior modification and for adopting a healthy lifestyle because of increased motivation and frequent access to medical supervision. We take time to counsel pregnant women about quitting smoking and carefully monitor their blood pressure and fasting glucose throughout pregnancy, yet some still balk at the suggestion that we should encourage these women to continue or start to exercise, even though physical inactivity is almost as dangerous to health as smoking, hypertension and diabetes.
Physical activity in pregnancy has been shown to benefit most women, by improving or maintaining physical fitness, helping with weight management and enhancing psychological well-being. There is now strong evidence to suggest that benefits of physical activity in pregnant women include improved muscular strength and endurance, cardiovascular function and physical fitness, decreased risk of pregnancy related complications such as hypertension and pre-eclampsia, reduced pelvic and back pain, fatigue, stress, anxiety and depression and decreased excessive gestational weight gain and post-partum weight retention. There are fewer delivery complications in women who are active during pregnancy and exercise can also help prevent and manage urinary incontinence associated with pregnancy and childbirth.
Despite the growing body of evidence regarding the benefits of exercise for the pregnant woman and her growing baby, a perception sometimes remains that exercise might be harmful to the mother and/or her unborn child. These unsubstantiated thoughts include misplaced concerns that blood flow to exercising muscles may result in inadequate foetal oxygenation and possibly even lead to miscarriage. The body of evidence suggests that the normal foetus compensates for any transient changes to blood flow during maternal exercise and is not at risk of harm, even in previously sedentary pregnant women. Light to moderate physical activity does not increase the risk of miscarriage or preterm delivery in uncomplicated pregnancies.
Pregnant women who want to continue or initiate an exercise program should be evaluated for medical and obstetric factors that may increase their risk for maternal or foetal complications. There are a small group of women in situations where the risk of physical activity during pregnancy is likely to outweigh the benefit. This includes those with ruptured membranes, incompetent cervix, hypertensive disorders of pregnancy, growth restricted foetus, multiple gestation above triplets, and those showing signs of preterm labour or placenta praevia after 26 weeks. There are also relative contraindications to exercise during pregnancy and specific situations where professional advice should be sought before exercising. Maternal core temperature of 39 degrees Celsius in the first 4-6 weeks of pregnancy has been shown to increase the risks of neural tube defects, however studies have shown that vigorous exercise at 60 – 70% VO2max in a controlled environment for 60 minutes doesn’t raise core temperature above 38 degrees.
Recommended exercise prescription in pregnancy follows the same principles and guidelines as nonpregnant people, modified to minimalise the risks to the mother and foetus. 30 minutes of moderate intensity exercise such as brisk walking is recommended 5 days per week, but as little as 10 minutes of light exercise per day to start with can be beneficial for previously sedentary women. The “talk test” can be used to monitor intensity, and women performing moderate exercise should still able to talk in sentences during physical activity. Activities with a high risk of falls or abdominal trauma should be avoided due to the risk of placental abruption and maternal injury. Exercises that require jumping and quick change of direction can stress joints and increase the risk of joint injury. Exercise performed lying on your back should be avoided after the first trimester due to potential restriction of blood return to the heart by the gravid uterus compressing the vena cava and subsequent maternal low blood pressure. Strength training can be performed but the focus should be on low intensity and high repetition. Scuba diving is contraindicated because the foetus is at increased risk of decompression sickness (the bends). Sky diving and hot yoga should also be avoided and people normally residing at low altitude should avoid exercise above 2500m (6000 feet) due to reduced oxygen availability.
A pregnant woman should stop exercising and consult her health care provider if she experiences any of the following warning signs; vaginal bleeding, regular, painful contractions, amniotic fluid leakage, new breathlessness before exertion, dizziness, headache, chest pain, muscle weakness affecting balance or calf pain or swelling. Prolonged exercise should be performed in a thermoneutral or controlled environment (airconditioning) with close attention paid to proper hydration and caloric intake. Further information can be found in the Sports Medicine Australia position statement on Exercise in Pregnancy and the Postpartum Period or the American College of Obstetricians and Gynecologists guidelines on Physical Activity and Exercise During Pregnancy and the Postpartum Period.
1. ACOG Committee Opinion No. 650: Physical Activity and Exercise During Pregnancy and the Postpartum Period. Obstet Gynecol 2015; 126:e135.
2. Barakat R, Pelaez M, Montejo R, et al. Exercise throughout pregnancy does not cause preterm delivery: a randomized, controlled trial. J Phys Act Health 2014; 11:1012.
3. Bo K, Artal R, Barakat R, et al. 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. Br J Sports Med 2016; 50:571.
4. Bo K, Artal R, Barakat R, et al. Exercise and pregnancy in recreational and elite athletes: 2016 evidence summary from the IOC expert group meeting, Lausanne. Part 2-the effect of exercise on the fetus, labour and birth. Br J Sports Med 2016.
5. World Health Organization. Global recommendations on physical activity for health. 2010, Geneva, Switzerland.