Your body is signaling that it's had enough if you feel:

• fatigue
• dizziness
• heart palpitations (your heart pounding in your chest)
• shortness of breath
• pain in your back or pelvis

And if you can't talk while you're exercising, you're doing it too strenuously.

It also isn't good for your baby if you become overheated because temperatures greater than 102.6? Fahrenheit (39? Celsius) could cause problems with the developing fetus — especially in the first trimester — which can potentially lead to birth defects. So don't overdo exercise on hot days.

When the weather is hot, try to avoid exercising outside during the hottest part of the day (from about 10 AM to 3 PM) or exercise in an air-conditioned place. Also remember that swimming makes it more difficult for you to notice your body heating up because the water makes you feel cooler.

Exercises to Avoid

Most doctors recommend that pregnant women avoid exercises after the first trimester that require them to lie flat on their backs.

Unless your doctor tells you otherwise, it's also wise to avoid any activities that include:

• bouncing
• jarring (anything that would cause a lot of up and down movement)
• leaping
• a sudden change of direction
• a risk of abdominal injury

Typical limitations include contact sports, downhill skiing, scuba diving, and horseback riding because of the risk of injury they pose.

Although some doctors say step aerobics workouts are acceptable if you can lower the height of your step as your pregnancy progresses, others caution that a changing center of gravity makes falls much more likely. If you do choose to do aerobics, just make sure to avoid becoming extremely winded or exercising to the point of exhaustion.

And check with your doctor if you experience any of these warning signs during any type of exercise:

• vaginal bleeding
• unusual pain
• dizziness or lightheadedness
• unusual shortness of breath
• racing heartbeat or chest pain
• fluid leaking from your vagina
• uterine contractions

Kegel Exercises

Although the effects of Kegel exercises can't be seen from the outside, some women use them to reduce incontinence (the leakage of urine) caused by the weight of the baby on their bladder. Kegels help to strengthen the "pelvic floor muscles" (the muscles that aid in controlling urination).

Kegels are easy, and you can do them any time you have a few seconds — sitting in your car, at your desk, or standing in line at the store. No one will even know you're doing them!

To find the correct muscles, pretend you're trying to stop urinating. Squeeze those muscles for a few seconds, then relax. You're using the correct muscles if you feel a pull. Or place a finger inside your vagina and feel it tighten when you squeeze. Your doctor can also help you identify the correct muscles.

A few things to keep in mind when you're doing Kegel exercises: