New Guidelines for Exercise During Pregnancy
The 2019 Canadian guideline for physical activity throughout pregnancy has been released. This involved a comprehensive assessment of the literature that examined 12 systematic reviews based on evidence from randomised controlled trials. It looked at exercise outcomes including pregnancy, labour and delivery complications, maternal mental health as well as foetal growth and development.
The previous guideline was from 2003 and was primarily based on expert opinion. There was minimal evidence available regarding the safety and potential benefits of exercise for pregnant women.
The review of the literature found that women who exercise during pregnancy had a 40% reduction in the risk of developing gestational diabetes, gestational hypertension and pre-eclampsia. They also had significant reduction in severity of depressive symptoms as well as a decreased risk of having a large baby. The most important finding was that there was no increased risk of having a miscarriage, small baby or pre-term birth.
Women who develop absolute contraindications during their pregnancy are encouraged to continue with their activities of daily living. However more strenuous exercise is not encouraged.
Absolute contraindications to exercise during pregnancy include:
Premature labour
Pre-eclampsia
Growth restricted baby
Ruptured membranes
Unexplained persistent vaginal bleeding
Placenta praevia after 28 weeks’ gestation
Incompetent cervix
High-order multiple pregnancy (e.g. triplets)
Uncontrolled type 1 diabetes
Uncontrolled hypertension
Uncontrolled thyroid disease
Other serious cardiovascular, respirator or systemic disorder.
Women who develop relative contraindications are encouraged to consult with health care provider to discuss the advantages and disadvantages in engaging in moderate to vigorous physical activity.
Relative contraindications include:
Twin pregnancies up to 28 weeks gestation
Gestational hypertension
Recurrent pregnancy loss
A history of spontaneous preterm birth
Mild/moderate cardiovascular or respiratory disease
Symptomatic anaemia
Malnutrition
Eating disorder
Other significant medical conditions
Six recommendations for exercise during pregnancy were found from within the evidence including:
All women without contraindications should be physically active throughout their pregnancy. Throughout means from conception until delivery.
Women should accumulate at least 150 minutes of moderate intensity physical activity each week to be able to achieve clinically meaningful health benefits and reductions in pregnancy complications. Examples of activity included walking, swimming, stationary cycling, yard work and vacuuming.
Physical activity should be accumulated over a minimum of 3 days per week however being active every day is encouraged.
Pregnant women should incorporate a variety of aerobic and resistance training activities to achieve greater health benefits. Adding yoga and/or gentle stretching may also be beneficial.
Pelvic floor muscle training (PFMT) may be performed on a daily basis to reduce the risk of urinary incontinence. Instruction on the proper technique is recommended.
Pregnant women who experience light headedness, nausea or feel unwell when they exercise lying flat on their back should modify their exercise position into a left side lying position or raise their head 30 degrees with 1-2 pillows.
In terms of high intensity exercise during pregnancy there have not been any specific studies to identify a maximum or upper limit to intensity, duration or frequency of exercise at this time.
Exercise during the first trimester of pregnancy
There has been a long-standing concern that exercise during the first trimester of pregnancy would increase the risk of having a miscarriage during this period or later in the pregnancy. The evidence reviewed suggested there was no increased risk of having a miscarriage for women who exercised within the guidelines. Women without contraindications may exercise from conception to delivery.
Safety precautions for exercise during pregnancy
It was strongly recommended that pregnant women avoid activities that have a high risk of falling or trauma to the belly including horse riding, down hill or water skiing as well as scuba diving. This is due to that there is no known safe depth for the foetus. There is concern that the foetal lung is too immature to be able to filter out nitrogen upon return to the surface. It was also recommended that women who were born and live below 25,000 metres avoid exercising above this altitude due to the lack of research available. The last precaution was to avoid exercise in excessive heat due to the concern of dehydration and the vasodilation that occurs which can increase the risk of the pregnant woman feinting.
Common misconceptions for exercise during pregnancy
Naturally during the time of pregnancy a mother is very cautious to avoid any activity that may cause any harm to her baby. The concerns around exercise was that it may cause miscarriage, having a pre-term birth or having a small baby. The findings of the systematic review do not support these concerns that there are any adverse effects to mother or baby.
The other common belief is that pregnant women should not exceed a heart rate of 140 beats per minute. This number stems from the original guidelines that were developed in 1985 based on expert opinion at the time and was then later removed.
Other important messages
There are going to be times or days when a pregnant woman may feel tired or unwell and meeting the exercise guidelines just isn’t possible. This is when it is important to listen to your body, take a day off when you have to however return to the guidelines as soon as possible.
It is known that meeting 150 minutes of moderate intensity exercise per week is associated with at least a 25% reduction in the odds of developing major pregnancy complications. However, being physically active below these recommendations will still have some benefits on health so some activity is better than none at all.
References
Mottola MF, Davenport MH, Ruchat S, et al 2019 Canadian guideline for physical activity throughout pregnancy. Br J Sports Med 2018;52:1339-1346.
British Journal of Sports Medicine Podcast with Margie Davenport; Bumping up physical activity throughout pregnancy. Episode 362.