We did not always know this. In the 1970s, pregnant women were told not to lift their arms overhead, carry anything, or rush anywhere, let alone exercise. By 1984, women were encouraged to be physically active, but to keep their heart rate below 140. The heart rate limit was abandoned by 1996. In 2002, pregnant women were advised to exercise most days of the week for 30 minutes.
Regular physical activity, such as walking, helps most pregnant women. Benefits include better fitness and improved blood glucose levels. It reduces the risk of gestational diabetes, caesarean section, high blood pressure and pre-eclampsia, childhood obesity, and postpartum depression.
Before 1984, doctors worried that exercise during pregnancy would cause babies to be born too small. Since then, studies have shown that babies may be born slightly smaller, but not so small that they are unhealthy or labelled as growth-restricted. The difference in birth weight averages less than half a pound (about 0.2 kilograms).
Exercise helps to control pregnancy weight gain. However, the effects are less than you might expect. Women who exercise regularly during pregnancy may gain one to two kilograms (2.2 to 4.4 pounds) less than without exercise. The quality and amount of the food you eat has more of an impact on weight gain than exercise does.
Ideally, women should begin exercising regularly before they become pregnant. Starting to exercise during pregnancy is also completely safe and recommended. Even women who are quite sedentary or not interested in exercise take a step in the right direction by doing some physical activity. For these women, the first goal might be as simple as reducing sitting time by 30 minutes a day.
Barriers to physical activity
Although barriers to activity exist, there are ways to overcome them.
This is an easy one. Pregnant women should exercise most days of the week. A good goal is five days per week, working up to seven if possible.
Intensity refers to how hard the exercise is. In the case of aerobic exercise, where the body is moving constantly, use the talk test to guide effort. You should be able to speak one sentence comfortably before needing to take a breath. If you cannot speak because you are out of breath, you are working too hard. If you can only spit out two or three words before taking a breath, you are also overdoing it.
With strength training, you should be able to do 10 to 12 repetitions of a weight-lifting activity comfortably. You should not feel as if your muscles are failing. (One repetition is one complete motion of an exercise.)
Three types of exercise are recommended during pregnancy. The first is aerobic exercise, where the body is moving constantly over a period of time. This includes activities like walking, running, swimming and aquasize, cycling, hiking, stair climbing, and rowing.
The easiest activity is walking. A 30-minute walk most days of the week is enough aerobic activity for a pregnant woman. Break walks up into smaller chunks if necessary. Two 15-minute walks are also a good option.
Women who run may continue to do so during pregnancy. Use the talk test as a guide for intensity. Running can be comfortable for some women until as late as the third trimester. Eventually, running will become uncomfortable. Protecting the pelvic floor is another consideration. The impact may cause discomfort or difficulty maintaining bladder control. It is not clear whether running damages the pelvic floor, but most specialists in this area advise against running later in pregnancy.
Women who have back and pelvic pain during pregnancy may find swimming and aquasize to be the best choice. The water supports the pelvis and belly very well. Many women report they feel no pain while in the pool.
Strength training is the second type of exercise recommended in pregnancy. It helps prevent injuries caused by the physical strains of baby care, such as lifting a car seat. Not enough women engage in this type of exercise during pregnancy. Do strength training twice a week. Use hand weights (small dumbbells), stretchy bands, or body weight (like leg lifts).
Step 1: Be less sedentary. Cut down on the time you spend sitting by 30 minutes per day.
Step 2: Be more active.
Work in the garden or climb the stairs more often.
Step 3: Try gentle exercise, like walking, until you are active up to 30 minutes per day.
If you do not know how to lift weights, see a fitness professional or a physiotherapist once to help you make a plan. Use a very low weight or even just your own body weight. For instance, a standing side leg raise helps build strength in the hip and buttock muscles. While standing, squeeze your buttocks together and lift the leg out to the side just a short way. Keep the toes pointing forward. Do three sets of 10 to 12 repetitions. Other examples include bicep curls and squats. The weight should be increased slowly, but the exercise should always feel comfortable when done at least 10 times. Breathing out as you lift prevents grunting and holding your breath. If you need to hold your breath or grunt, the exercise is too hard.
Many pregnancy resources recommend avoiding exercises lying flat on your back after 13 weeks. This recommendation is outdated. The concern was that the weight of the growing baby would compress large blood vessels bringing blood back to the heart from the body. This could cause a drop in blood pressure, leading to symptoms of dizziness and nausea. If this happens, it is most likely to occur near the end of pregnancy when the baby is biggest.
The good news is that the symptoms resolve immediately with a change of position. Feeling unwell for a few seconds is not harmful.
Flexibility training is the third type of recommended exercise. Also called stretching, this type of exercise is often done by pregnant women, especially in prenatal yoga classes. Although stretching feels good and may ease some pregnancy discomforts, it does not qualify as either aerobic or strength-training activity. Many women hope that stretching will help the common low back and pelvic discomforts of pregnancy. They may actually be better served by adding strengthening exercises for their low back and buttock muscles, rather than doing more stretching. This does not mean that pregnant women should abandon stretching. Rather, they should not overvalue its effect.
This guideline refers to how long an exercise session should last. For aerobic exercise, 30 minutes is the goal. If you exercised regularly before pregnancy and are used to doing more, it is okay to continue aerobic sessions for as long as 60 minutes. If the exercise intensity is moderate (but still within the talk test parameter), women can build intervals into their workouts. For instance, work harder for five minutes, then back off in an easy recovery period for three minutes, followed by another five minutes of harder work.
Other things to consider
For women who are motivated and fit heading into pregnancy, discussing goals with a medical practitioner familiar with pregnancy exercise is a good idea.
Hydration and temperature are important during pregnancy. Exercising in warm weather can be more difficult. Drink more water than usual to maintain adequate hydration. On the warmest days of the year, shorten the duration of workouts. Adjust the timing of workouts to take advantage of cooler mornings or evenings. Along the same lines, exercising in hot conditions, such as hot yoga, is not advised in pregnancy.
Although exercise is almost always good in pregnancy, there are exceptions. Talk to your doctor about whether you have any reason not to exercise. Pregnant women who have the following conditions absolutely must not exercise:
Similarly, there are some activities that are not recommended in pregnancy. This is not the time to try scuba diving, skydiving, hot yoga or marathon running. After the first trimester, avoid any activities that put you at risk of trauma, such as horseback riding and team sports. This is because falling, collisions or projectiles could put the pregnancy at risk. A soccer ball to the belly is not a good idea at 18 weeks of pregnancy.
If you are thinking about becoming more physically active, start with an easy aerobic activity that you will enjoy, such as walking. Try it for a short period of time, working up to a goal of 30 minutes per day. Not all days will be good ones. If you start an exercise session and feel awful, it is okay to stop. Try again the next day. As well, you may not always feel like exercising. On those days, you will have to push yourself. Do five minutes. If you still feel awful after five minutes, then stop, but the rule is that you must try again the next day.
If exercise is not enjoyable, try some tricks to make it better. Choose a different activity, listen to your favourite music, ask a friend to join you, or wear a step counter to help motivate you. If so inclined, track your exercise to see how the time adds up. Put a check mark on a calendar for each day that includes physical activity. And most of all, enjoy it – physical activity is a gift to yourself and your baby.