Exercise during the second trimester of pregnancy can be very important in keeping up your energy level and helping you sleep well at night. It can also help prepare your body for labor and prevent too much weight gain (Mayo Clinic, 2010). The key to exercise during pregnancy is to take it “slow and steady.” You should always warm up before you exercise and stop if you feel short of breath or are in pain. Slow down your pace before you come to a complete stop. It is always wise to get your healthcare provider's stamp of approval before you begin or change an exercise program while pregnant.
Exercise Frequency and Duration
It is safe to exercise daily during the second trimester. If you enjoy long workouts, pay attention to your body’s signals and stop when you are tired. You may need to shorten or simplify your workouts over time as your belly expands and your pregnancy symptoms change. Most women can comfortably manage 30 minutes of moderate physical activity (such as walking or swimming) three to seven days each week without difficulty. Depending on how much you exercise, you will also have to increase your daily calories above the extra 300 needed during the second trimester (Wang & Apgar, 1998).
For health and safety reasons, keeping your heart rate in a good range is important. Exerting yourself moves blood to your muscles and skin and may move less to your uterus. If exercise is too strenuous, there is a risk that less oxygen will reach the baby.
When you exercise, make sure you stay below 60 percent of your maximum heart rate. For most women, this means you should maintain your heart rate at less than 140 beats per minute. If you stay below 60 percent of your maximum heart rate, you don't need to worry about harming your baby when you exercise. Remember to avoid overheating and keep yourself hydrated during any exercise.
Safety Warnings for Second Trimester Exercise
In addition to keeping an eye on your heart rate, pay attention to your body’s signals. If you experience any of the following symptoms, stop exercising immediately, as you may be exercising too much or too hard:
- dizziness or light-headedness
- nausea or vomiting
- overheating or dehydration
- unusual vaginal discharge or bleeding
- belly pain
- lower back pain
Call your doctor if any of these symptoms worry you or do not resolve within 15 minutes of stopping your physical activity.
Aerobic activities such as running and swimming, relaxation techniques, and strength training are all appropriate during the second trimester of pregnancy, as long as you are aware of your limits and follow simple guidelines for safety. Even if you did not exercise before pregnancy or during the first trimester, you can safely begin a simple exercise routine during the second trimester of pregnancy. Some of the gentlest ways to begin getting exercise during pregnancy are through walking or swimming.
As you progress in pregnancy, your body produces a hormone called relaxin, which is responsible for loosening joints in preparation for a growing baby, labor, and delivery. As your joints become looser, you are at more risk for sprains and strains. Your increased weight and the change in your center of gravity may cause you to lose your balance, also putting you at greater risk for injury. As your second trimester progresses, it is best to avoid exercises that involve extreme stretches or high-impact activities—like aerobics and running—that put a lot of stress on your joints and put you at risk for falls.
Month-by-month guidelines for exercise during the second trimester are given below:
- Weight training: As you begin your second trimester, your total blood volume has increased and the placenta and baby are growing. When you stand, blood can pool in your legs, causing you to become lightheaded or dizzy. For this reason it may be safer to do weight training exercises while seated. Always keep your breath steady during weight training to avoid straining your muscles and blood vessels.
- Jogging and running: If you are a runner, you can safely continue to run in moderation. During your second trimester your uterus gets larger, causing your center of gravity to shift. This change makes you more likely to lose your balance. Run on flat ground with as few obstacles as possible.
- Yoga: As you slowly get bigger and your joints loosen, your balance may be affected, putting you at risk of injury. Pay attention to your body and only do as much exercise as is comfortable. Your breathing should stay smooth, and if you find you cannot breathe easily and smoothly during positions, think about shifting into an easier version of the position, stretching or extending less, or staying closer to the floor. You may also wish to use a chair or wall for balance during standing poses. Leg lifts, back bends, lying on the belly, and poses that stress the abdomen or pelvic floor should also be avoided or modified by a teacher trained in prenatal yoga techniques (Plakans, n.d.).
- Swimming and Water Aerobics: If you are a swimmer, you should be able to continue swimming into your second trimester without any difficulty. If you are new to swimming, start slowly by swimming gently for short periods of time, taking caution not to overexert yourself. Work up to longer workouts if you desire. Moderate water aerobics may also be helpful for previously inactive women (Baciuk, Pereira, Cecatti, Braga, & Cavalcante, 2008). This activity may even reduce your desire for analgesia during labor.
As your belly gets bigger, you may find that your center of gravity has shifted and you're not as agile as you once were. Compensate by being more careful when you step. When you reach 20 weeks, you should stop exercises that require you to lie on your back (like some weight lifting or yoga poses). As your uterus increases in size, lying on your back can put pressure on the inferior vena cava, the large vein that runs vertically the length of your abdomen and is responsible for returning blood to the heart.
- Walking: As your gait changes because of the changes in your body shape, be sure to focus on your posture when walking and keep your hips tucked under to prevent arching your back due to the increasing amount of weight you're carrying in front. When you feel out of breath, slow down or stop and rest. You shouldn't be huffing and puffing.
- Yoga: As your pregnancy progresses and has a larger impact on your activity, think about joining a yoga class specifically for pregnant women or buying a book or video of yoga poses that are safe for pregnant women.
- Swimming: If you are a swimmer, you should be able to continue swimming into your second trimester without any difficulty. If you begin to get short of breath during swims, try slowing your pace and staying near the edge or shallow end of the pool.
Your blood volume increases by 40 percent during pregnancy and your cardiac output (heart rate times the amount of blood pumped per beat) increases by 30–40 percent. During exercise, your heart rate increases even more. Although research shows that women who exercise regularly have no increased risk of problems with their pregnancies, the key is still moderation. Don't push yourself too hard. Keep yourself hydrated and cool.
- Weight training: You may want to decrease the duration or frequency of your workout, depending on how you're feeling. You may also be more comfortable with lighter weights. If you use free weights, be very careful to avoid blunt injury to the abdomen from dropping weights. Do not hold your breath during repetitions, and do not lie on your back.
- Yoga: Now that you're at the end of your second trimester, you may need extra balance support when doing standing poses. Avoid poses that stretch the abdominal muscles or that require you to lie on your back. Bend from your hips. If you feel discomfort, stop and reevaluate if there's an easier way to do the position.
In addition to the standard second trimester exercises (such as walking, yoga, and swimming), there are many other activities you can safely do for fitness. Follow the guidelines from above about warming up and taking care of yourself when performing any activity. If you are unsure how to safely perform these activities or do not know if they are safe for a particular health condition, ask your healthcare provider before beginning.
Try the following activities to break a sweat during the second trimester:
- stationary bicycling (recumbent if needed)
- rowing (in a canoe or on the machine at the gym)
- housework (sweeping, vacuuming, gardening, window-washing, and even mowing the lawn)
- sex (avoid lying on your back) (Mayo Clinic, 2012)
- light aerobic workout courses (Harper, 2012)
- tai chi (same limitations as yoga poses)
- ballroom, Latin, and jazz dancing (avoid back bends, jumping, and spins)
Do not hesitate to reduce the length or intensity of your workouts if you are having difficulty or do not have the energy to continue. Stay hydrated by drinking a glass of water before, during, and after exercise. Regardless of your chosen exercise, always remember to keep tabs on your health symptoms during and after your workouts.
Don't worry if your doctor has suggested that you not exercise. Despite the many benefits of exercise, there is little harm in not exercising during pregnancy. Many women who do not exercise during pregnancy still have healthy babies. Some pregnancy-related conditions may make it dangerous for you to exercise, such as placenta previa, preeclampsia, or intrauterine growth retardation (Wang & Apgar, 1998). If you have a history of miscarriages or an insufficient cervix, your healthcare provider may recommend that you not exercise. The benefit of protecting your baby by not exercising for medical reasons outweighs any feel-good vibes from a few laps in the pool.