By Barbara C. Bourassa

If there is one constant in being pregnant, it's the fact that most women have to endure a never-ending stream of changes, including the growing bulge in their bellies, fluctuating energy and moods, and food cravings.

In many ways, you're a hostage to those changes as your body adapts in its own unique way to the baby growing inside. Luckily, though, there's a tried-and-true formula for riding out these changes that's probably already familiar to you:

The triangle of exercising, eating right and getting enough sleep.

The first corner of the triangle: exercising

If you already have a regular exercise program and you get pregnant, there's no reason to give up that routine unless you have a health condition that would prevent continuing the exercise.

Always check with your OB/GYN to be sure, particularly if you suffer from any of the following conditions:

•  heart or lung disease;

•  obesity;

•  severe diabetes;

•  thyroid disease;

•  pregnancy-related high blood pressure.

A regular exercise program will help you fight off tiredness and moodiness, especially in the first trimester. It will also help you sleep better, which is especially important later in the pregnancy. In addition, keeping fit can make it easier to get back in shape after childbirth.

What's more, according to information from the American College of Obstetricians and Gynecologists,  exercising at least 30 minutes a day may help prevent backaches, gestational diabetes, constipation, and varicose veins.

Unless you're extremely fit, now is not the time to learn to ski or to start training for your first 5K run. For the most part, experts recommend low-impact or moderate exercise, such as:

•  walking;

•   swimming;

 •  low-impact aerobics;

•  gardening;

•  dancing.

There are a few sports that are considered dangerous for pregnant women, mostly because of the risk of falling, including skiing and horseback riding. Also, all moms-to-be should avoid scuba diving.

As your pregnancy progresses, you should change your exercise habits to accommodate your changing body.

Keep in mind that your center of balance will change, and your growing belly might get in the way of, say, hitting a golf ball or riding a bicycle.

The second corner of the triangle: eating right

Eating right while you are pregnant is critical for several reasons. First, eating a balanced, healthy diet helps ensure that your baby will get the nutrition he or she needs to develop properly.

Second, eating right may give you more energy, and it may help prevent unnecessary weight gain or mood swings from low blood sugar during pregnancy.

Eating for two doesn't mean losing control, however. On average, you only need 300 to 350 additional daily calories throughout your pregnancy, and these should come from wholesome choices, such as fruits and vegetables, lean proteins, healthy fats and whole grains.

Some health experts advise that all pregnant women should also take a multivitamin to ensure adequate levels of important nutrients, such as folic acid, iron and calcium. They also should avoid alcohol and smoking.

The third corner of the triangle: Getting enough sleep

It sounds pretty basic, but for many women, getting enough sleep while pregnant is difficult. According to the 2007 National Women and Sleep poll, 40 percent of pregnant and 55 percent of postpartum women reported getting a good night's sleep a few nights a month or less.

One way to counter this, according to experts at the National Sleep Foundation, is to plan for sleep the way you plan and schedule the rest of your life. Even an extra 45 minutes of sleep per night can mean the difference between a happy pregnancy and an unhappy one.

Some advice that worked for me: take naps whenever possible, especially as the pregnancy progresses. If necessary, curtail your social activities at night to get the shut-eye your body needs.

And watch for signs of unusually persistent tiredness or darker-than-usual moods, because these might be a signs of something more serious. If in doubt, be sure to check with your OB/GYN for advice.
While nobody can predict how your body will handle pregnancy, taking control of the things you can control will certainly give you a leg up on the unpredictable events that may occur. And you'll feel healthy along the way.

Barbara C. Bourassa is a freelance writer and editor living in North Andover, Mass.