• Running/jogging: If you're a runner, you can keep on running. Competitive runners often maintain their training during pregnancy. But if you haven't been running for a while, starting up during pregnancy doesn't make sense. You put yourself at risk of musculoskeletal injuries — knee and hip problems and the like — especially after the body's center of gravity shifts significantly in the third trimester. Better to try brisk walking, 30 to 60 minutes a day, which can also raise your heart rate to fitness range. Many runners find that later in pregnancy, fatigue keeps them from going their usual distance.
• Overheating: Try not to overheat or become dehydrated, and if you feel fatigued, dizzy, faint, or nauseous, by all means stop. On very hot or humid days, don't exercise outdoors.
• Stair-climbing machines: Stair climbing is weight-bearing, but most machines help lighten the load so that it isn't as weight-bearing as aerobics or running. And the stationary machines pose little risk of falling. As your stomach grows, you put more stress on your back muscles. But all things considered, stair climbing is an excellent form of exercise for pregnant women, especially if the room you're in gets plenty of fresh air.
• Stretching and body sculpting: These are fine as long as you don't do them flat on your back or overextend. You don't get any cardiac benefit, but stretching does help you maintain muscle tone and flexibility, which can come in handy during labor and delivery. Kegel exercises, which involve targeting and contracting the muscles of the pelvic floor (around the opening of your bladder and vagina), may not help so much during pregnancy. But afterward, they can make it easier for your pelvic muscles to return to normal, and they may prevent problems with urinary incontinence later in life.
• Swimming: If you swam before you got pregnant, keep swimming now. In fact, swimming is one of the best exercises a pregnant woman can do because it puts no stress on your joints and poses little risk of overheating or losing your balance and falling. However, most doctors advise that you avoid scuba diving because the dramatic pressure changes could have adverse effects on the baby.
• Yoga: Most forms of yoga are fine during pregnancy and may even relieve some of your stress. Many yoga teachers offer special pregnancy classes, but regular classes are also fine. Just avoid lying flat on your back or overstretching.

Excerpted from Pregnancy For Dummies™, published by John Wiley & Sons.

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