Labour can be like a marathon – it takes hours and leaves you sore and exhausted. So surely it makes sense to use that nine-month lead-up to stay fit. But how much exercise is enough – or too much? “Labour is the most gruelling endurance event you’ll ever perform as a woman,” says Edwina Griffin, a Sydney-based personal trainer with FitMum, which provides exercise and nutrition information for expectant mums, “so it pays to get in training.”

According to Sports Medicine Australia, there’s no evidence that moderate-intensity aerobic activity during pregnancy has any negative effects on your developing baby or the birth. So if your pregnancy is healthy and uncomplicated, you can enjoy all the feelgood benefits of walking, swimming, yoga, aqua aerobics and some kinds of dance, such as bellydancing, right up until the birth.

Three to four times a week is good. “Limit more vigorous exercise to 20-minute sessions and keep your heart rate to about 140 beats per minute,” says Griffin. “If you want to include weights, drop your weights down from your pre-pregnancy levels and increase your repetitions.”

Pregnancy is not a time to increase your fitness or take up higher intensity exercise such as running. However, if you were running before you conceived, you can continue to run during your pregnancy but you’ll need to be monitored by your doctor.

Before you start exercise of any kind, discuss your plans with your doctor and always let your instructors know you are pregnant. If you have hypertension or diabetes, you’ll need medical supervision. “Women with a multiple pregnancy, at risk of a premature baby, with preeclampsia, heart disease or infectious illness may need to avoid exercise altogether,” says Dr Carolyn Broderick, director of the sports medicine program at the University of NSW. After the first three months, Broderick advises expectant mums to “avoid contact sports such as netball or basketball, collision sports such as rugby and some martial arts, and activities where there’s a risk of falling, such as cycling and horse-riding.” Pay special attention to staying cool and hydrated (sports drinks will keep your blood sugars up). Your ligaments and muscles soften during pregnancy making you prone to sprains and strains so be sure to stretch and warm up. After four months, avoid exercises that involve lying on your back, says Griffin – you’ll feel dizzy and faint as pregnancy lowers your blood pressure.

In addition to increased endurance, regular exercise can also improve posture, mood and sleep, as well as reduce back pain and help ward off gestational diabetes and post-natal depression. But while fit women are better equipped to cope with long labours, says Broderick, “it’s a myth that they have easier labours.”

Visit vicfit.com.au and www.health.nsw.gov.au for more information.