Gone are the days when doctors worried that aerobic excercise might place the developing fetus or mother-to-be at risk. Modern medical professionals now widely acknowledge the many profound health benefits that cardiovascular exercise during pregnancy provides for you and your growing baby.


Old Beliefs about Exercise and Pregnancy

Twenty years ago, science had conducted very little research on the effects of exercise during pregnancy. Without hard factual-evidence, doctors erred on the side of caution, and advised a sedentary lifestyle for their pregnant patients. Prior to 2002, doctors advised women to limit their heart rates to no more than 140 beats per minute during pregnancy.


Current Recommendations about Pregnancy and Aerobic Exercise

The American College of Obstetricians and Gynecologists (ACOG) no longer places restrictions on heart rate during aerobic sessions. Larger, more comprehensive studies on aerobic exercise during pregnancy have shown that women do not need to limit their sub maximal heart rate. Complete current ACOG guidelines for exercise during pregnancy can be accessed on their Web site.


Research Finds No Link between Aerobic Exercise in Pregnancy and Miscarriage

Today, we know that physically fit moms have healthy pregnancies, and give birth to healthy babies. Numerous scientific studies have shown that, among healthy women, no link exists between moderate to vigorous levels of aerobic exercise and miscarriage or other pregnancy complications. In fact, fit mothers-to-be who engage in regular cardiovascular exercise have substantially lower incidences of back pain, gestational diabetes, depression, labor interventions, caesarian births, and other problems associated with pregnancy.


Benefits of Aerobic Exercise During Pregnancy

•	When you are fit, you’re more likely to give birth to a leaner baby.
•	With regular aerobic exercise, the size of the placenta increases, and so does its capacity to exchange oxygen and CO2, and nutrients and waste products.
•	Babies born to fit moms have greater cardiovascular capacity from the start.
•	Lean babies are less likely to become overweight or develop diabetes as adults.
•	If you breastfeed, improved immune function will carry over to your baby for the first several months of life.
•	Prevents excessive weight gain during pregnancy, which reduces both your risk of gestational diabetes and your baby’s risk of developing diabetes as an adult.
•	Fit moms bounce back into shape after delivery much more quickly than sedentary women.
•	Provides needed stamina for labor and delivery.

Best Aerobic Activities during Pregnancy

•	Fitness walking
•	Hiking (low altitude)
•	Low-impact aerobic classes
•	Step aerobics (low step level)
•	Nia, or other free-form movement classes
•	Treadmill
•	Elliptical trainer
•	Recumbent bicycle
•	Swimming
•	Aqua aerobics
•	Dancing (low impact)
•	Jogging

NOTE: Jogging may need to be replaced with a lower-impact exercise in the last trimester.


How Much Aerobic Exercise Is Safe?

ACOG recommends the minimum activity level of 30 minutes of walking on most days of the week for all healthy pregnant women, including those who have been sedentary. In general, fit women may maintain or even increase their cardiovascular capacity during the first half of pregnancy.


Putting Limits on Aerobic Exercise—The Third Trimester

Your level of perceived exertion for a given fitness activity will increase as pregnancy advances, due to your baby’s need for greater oxygen and nutrients. What was once an easy workout might prove to be too challenging by the third trimester. To avoid overtaxing your body, slowly reduce the intensity of your workouts as labor and delivery nears.

The increasing weight of the baby and continual stretching of the round ligaments—the ligaments that connect to the uterus—can make impact exercise, such as jogging, uncomfortable in the last trimester. Fitness walking, either outdoors or on a treadmill, indoor cycling, or the elliptical trainers are all good non-impact aerobic alternatives.

Women should continue to monitor their levels of perceived exertion during cardiovascular exercise throughout their pregnancies. Stay within the range where you feel your exertion level is “somewhat difficult.”


When Not to Increase or Start Aerobic Activity

The size and functional capacity of the placenta—the ability to exchange oxygen and CO2, and nutrients and waste products—is set midway through pregnancy because the placenta stops growing at 20 weeks. Therefore, you should not try to increase your aerobic capacity, or start an aerobic program, in the last half of pregnancy.

If you have kept a moderate to strenuous aerobic exercise program up to this point, switch to an aerobic maintenance program during the second half of pregnancy. As your due date approaches, reduce the intensity of your workouts to counterbalance your baby’s increased need for oxygen as she grows.

If you were previously sedentary or relatively less fit, a fitness walking program will provide many of the same health benefits (though to a lesser degree) as a more intense aerobic workout, and can be done safely throughout your pregnancy.


Pregnancy Exercise for Sedentary or Less-Fit Women

Women who work full-time at desk jobs often find it difficult to schedule the 30-minute block of time for fitness walking that the American College of Obstetricians and Gynecologists (ACOG) recommends. Fortunately, you can achieve the same health benefits if you break your daily workout into shorter sessions throughout the day.


Tips for Fitness Walking

Tips for Very Fit and Athletic Moms-to-Be

If you are very fit, you may exercise within the range of "somewhat difficult to difficult" in the first half of your pregnancy, and then shift down to "somewhat difficult" in the second half. Athletes may continue interval training in the first half of pregnancy. If you are very athletic and want to continue more strenuous workouts, monitor your resting heart rate to prevent over-training.

How to Monitor Your Heart Rate to Prevent Over-Training

Post Exercise Cool-Down Critically Important during Pregnancy

While you're pregnant, the cool-down phase (when heart-rate gradually lowers) of aerobic conditioning sessions must be significantly lengthened to prevent pooling of blood in the lower extremities, dizziness, or fainting. These effects can occur because pregnancy hormones relax blood vessels, resulting in lower blood pressure and increased blood flow to the extremities.


Post Exercise Cool-Down Tips for Pregnant Women

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