While pregnancy can be uncomfortable at times, your impending motherhood does not give you a nine-month excuse to be a couch potato. In fact, maintaining—or starting—a regular fitness regimen while you are pregnant can have numerous benefits.

The earlier you start working out during pregnancy, the better you'll feel in the long run. Again, some things don't change after conception. Consistent exercise was and still is the best way to keep your heart strong and healthy and your muscles toned and lean. Exercise can also provide relief for many of the aches and pains that accompany pregnancy. Morning sickness, constipation, and sore legs and back can often be helped with a little movement. Exercise may also contribute to a shorter and easier labor - now that's worth sweating for.

Yes, working out is a positive thing to do for both you and your baby, but this is not the time to train for your first marathon. If you had a moderate exercise routine before you were pregnant, you should continue it - following the guidelines listed below and after talking to your health care practitioner, of course. But if you were not active before, it's important to introduce exercise into your (pregnant) life slowly.

Tips for Pregnant Exercisers

• Avoid overheating (very important during the first six weeks of pregnancy).
• Skip exercises that require you to lie on your back for long periods - this may compromise blood flow to your heart, which is not a good thing.
• Your continually shifting center of gravity may make it difficult to practice sports that require balance like surfing, riding horses, and skiing and snowboarding. It's also common sense to avoid anything that may put your abdomen at risk of being injured—sorry, dodgeball is out—and high-impact exercises that can strain your already overextended joints.
• Just like you did before you were pregnant, be sure to bring water to every workout and stay hydrated.
• Eat well. A well-rounded diet with the proper amount of carbohydrates, proteins, fruits and vegetables will help you exercise more efficiently and safely.
• Calculate your peak heart rate (your health care practitioner can help). Regular heart rate monitoring throughout your workout will ensure that you stay at a safe level.

Workouts that Work

There are a few sports that many pregnancy experts encourage women to avoid for those nine months, but it's up to you to make choices that are best for you and your baby. Activities that require balance, increase your risk of injury, or alter your body temperature (think snow sports) may be dangerous for pregnant women.

Vigorous physical activity is not off limits for pregnant women who were vigorously physical pre-pregnancy. Runners can keep running, weight trainers can keep training as long as they monitor their overall sense of wellbeing and talk to their practitioner if any changes or concerns arise.

For those looking for a moderate exercise regimen, the following activities are ideal for a fit pregnancy:

• Swimming is best for pregnant women - it's non-weight bearing (that whole no gravity thing really helps here) and also keeps you cool.
• Biking is non weight-bearing too, but cycle lightly during the later stages of your pregnancy as your growing tummy may throw you off balance and off of your bike.
• Walking is another excellent workout. Depending on your level of fitness, you can walk briskly or moderately.
• Yoga is a wonderful exercise for pregnant women. Regardless of your level of experience, you can benefit from the practice's calming and invigorating asanas - or postures. As with all forms of fitness, pregnant women should take precautions when practicing yoga. It's important to ask your instructor for pregnancy modifications and to asses your pre-pregnancy yogic ability before jumping into a challenging poses like Sirsasana (headstand) or Adho Mukha Vrksasana(headstand). Many yoga centers also offer specially designed prenatal classes via Discovery Health, Harvard Health Services, Mayo Clinic, and Yoga Journal