Staying fit during pregnancy helps keep up your energy level, controls your weight gain so it doesn’t become excessive, and helps build up the stamina you’ll need for childbirth and post-delivery recovery. What matters is that you choose a type of exercise that you enjoy and that you’ll stick with. If you have any doubt about whether a certain form of exercise is right for you, be sure to check with your doctor!

Safe exercises:
Brisk walking
Low-impact aerobics
Stationary cycling
Swimming or water aerobics

Acceptable exercises:
Racket sports
Cross-country skiing
Golf
Weight training
Bowling
Hiking
Jogging

High-risk exercises:
Sail boarding
Downhill skiing
Surfing
Horseback riding
Scuba diving
Waterskiing  

Some things to keep in mind, regardless of how you choose to exercise:
Drink water: Lots of it.
Wear an appropriate bra.
Stop if you feel very tired, dizzy, or nauseated.
Warm up and cool down. 
DON’T exercise in extreme heat or humidity.
DON’T exercise if you become short of breath.
DON’T use a hot tub or sauna.
DON’T exercise while lying on your back after your third month.