Pregnancy and exercise

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Studies show expectant mothers who exercise have a lower risk of developing conditions like gestational diabetes, maintain better musuloskeletal fitness and circulation, handle labour better and recover more quickly from giving birth.

But only one in six pregnant women are actually exercising enough. Before you grab your runners and dash out the door: nine months of pregnancy means nine months of progesterone flowing through your body - loosening things up in preparation for birth. A side-effect of this is a reduction of muscle tone and an increase in injury risk. So always warm-up and cool down with at least 10 minutes of stretching every time you exercise.

First trimester

Don't do anything to overheat your body (like Spin), says Women's Health health expert Dr Ginni Mansberg. "This has been linked to miscarriage," she explains.

She also recommends you get a heartrate monitor, and not let your heartrate go over 140bpm. Pregnancy boosts your resting heartrate and makes less oxygen available for muscles, so pre-pregnancy heartrate recommendations are no longer reliable. According to Sports Medicine Australia, you can still play "collision" sports like soccer and contact sports like netball.

Second trimester

Anything that raises your heart rate over 140 should be limited to 20 minutes. Sports Medicine Australia advises that from four months you should avoid anything involving rapid changes of position, like going from lying to standing, because the development of blood vessels supplying the growing placenta will cause your blood pressure to fall, increasing your risk of dizzy spells. You should also avoid leg exercises done while lying on your back - the weight of the foetus can impede the return of blood to your heart.

Third trimester

If you're already a keen exerciser, you might want to keep up your routine, but Dr Mansberg recommends you don't go too hard, no matter how fit you are. "Overstressing your body in the third trimester can cause rupture of the uterus or placental abruption, though this would only happen in an extreme case, such as if you ran a marathon." Running is not recommended in the third trimester, and weight-lifting is also considered dangerous at this stage.

"Swimming is excellent," says childbirth expert Dr Miriam Stoppard, author of Conception, Pregnancy and Birth. "It tones most of your muscles and is a good way to build up stamina. Your body weight is supported by the water, so you're unlikely to strain or injure muscles or joints." Avoid sit-ups, cycling, skiing and horseback riding at this stage.

What about yoga?

You may have heard that women shouldn't do yoga in the first trimester. "I think this is garbage," says Dr Mansberg. "But if you do take a yoga class, be sure to let the instructor know you're pregnant beforehand."

Yoga can be a great way to keep your muscles in shape while you're pregnant, and it can also help you to breathe and relax. If you've never done yoga before, Women's Health yoga expert Nicole Walsh recommends you go to a specific pre-natal class taught by a qualified teacher.

Also, "Less is more!" Walsh says. "Focus on other yogic techniques like meditation and pranayama, especially in the third trimester."

She also warns against doing any twisting or upside-down poses, strong backbends or strong forward bends.

"Just listen to your body," Walsh advises. "If it doesn't feel good, then it's not doing you good."