Mums-to-be, do not use pregnancy as an excuse to take a nine-month hiatus from exercise.

"Giving birth is an intense aerobic activity. The uterine muscles contract rhythmically over a potentially long and unpredictable length of time," said Dr Anne Hagarty, a consultant obstetrician and gynaecologist at Mount Elizabeth Hospital.

"The uterus is essentially running a marathon. The more comfortable a woman's body is with regular exercise, the better she will be at handling this level of physical activity," she added.

Previously, doctors had advised pregnant women against over-exertion or starting an exercise programme if they led a sedentary lifestyle.

There were indeed concerns, Dr Ong Wee Sian, head and consultant sports physician in the sports medicine service at KK Women's and Children's Hospital (KKH), explained.

Among the concerns: a rise in the expectant mother's body temperature may disrupt the embryo's development; oxygenated blood and nutrients would be directed to the mother's muscles instead of the foetus; the foetus may suffer direct trauma; and the secretion of certain hormones during exercise may increase the risk of premature labour.

However, Dr Ong said: "Recent studies on regular aerobics and strength exercise regimen during pregnancy show no increase in early pregnancy loss, late pregnancy complications or abnormal foetal growth."

Therefore, there is no need to refrain from physical activity or exercise at any stage of the pregnancy as long as the pregnant woman feels comfortable and well, he said.

Benefits of exercise Working out during pregnancy - apart from achieving the objective of improving physical fitness and strength to better withstand labour pains - can benefit expectant mothers in other ways.

Dr Ho Hon Kwok, a consultant obstetrician and gynaecologist at H K Ho Women & Fertility Clinic at Mount Alvernia Medical Centre, said: "Regular exercise helps reduce backaches, constipation, bloating and swelling and may help to prevent or treat gestational diabetes.

"It increases the woman's energy level, improves her mood and posture and helps her to sleep better too."

Financial controller Catherine Williams, 38, accepts this advice.

The fourth-time mother, who is 32 weeks pregnant and goes to the gym twice a week, said: "I didn't exercise during my last three pregnancies.

"But exercise does make a difference. With my last pregnancy, I had to go on a very strict diet from the 18th week on as I had developed gestational diabetes. Now I'm experiencing it only in my 32nd week."

She added: "The problem of water retention has been a lot better this time. Before, I wouldn't have been able to see my ankles by now. Now, only one ankle is a little swollen."

Dr Kwek Hwei Min, a sports medicine registrar with the Changi Sports Medicine Centre at Changi General Hospital, said pregnant women who engaged in recreational physical activity reduced their risk of gestational diabetes (a condition in which pregnant women not previously diagnosed with the disease exhibit high blood glucose levels) and pre-eclampsia (pregnancy-induced hypertension) by about 50 and 40 per cent respectively, compared to inactive women.

Exercise caution

While exercise is generally beneficial to expectant mothers, doctors Mind Your Body spoke to cautioned that pregnant women should seek medical advice before embarking on any exercise programme.

This is especially so for those with medical conditions like serious heart or lung diseases, uncontrolled or poorly controlled Type 1 diabetes, thyroid diseases and multiple gestations like twins or triplets.

Dr Kwek advised women who have been inactive before getting pregnant to delay exercising until the second trimester.

Dr Hagarty added that swimming, walking and pre-natal yoga are good choices for an inactive, pregnant woman wanting to begin exercising.

She said: "I usually suggest that each new exercise be done not more than once every three days and not less than once a week.

"She can exercise between 20 and 40 minutes within her comfort zone. It is important not to push too hard and to allow time for recovery."

Dr Ho said that beginners can start with five minutes of exercise a day and work slowly up to 30 minutes daily.

He also emphasised the importance of warming up and cooling down after exercise.

Those who have been exercising regularly before their pregnancy can continue with their preferred frequency of exercise although the intensity should be reduced.

Athletes like marathon runners can continue with their training but should reduce the intensity in later months.

Dr Choo said of marathon runners: "Footwear is especially important because in long distance running, the woman's increasing weight and her changing centre of gravity will impact her joints."

Seek doctor's advice As for those with conditions like high blood pressure or diabetes, doctors said they should check with their physician before starting exercise.

Dr Hagarty said: "Exercise is an excellent way to improve diabetic control, symptoms and pregnancy outcome so I encourage all my diabetic patients to exercise regularly throughout pregnancy.

"However, they must be aware of the potential for low blood sugar levels during and after exercise. I always recommend they take a low glycaemic snack during and immediately after exercise to prevent this."

Dr Choo Wan Ling, a consultant obstetrician and gynaecologist at Pacific Healthcare Specialist Centre, said high blood pressure in pregnancy can increase the risk of foetal growth restriction.

She said: "Exercise may reduce blood flow to the placenta further. In the first half of the pregnancy, it should be safe to do light exercises like walking or swimming. After that, it would be safer to rest more."

junec@sph.com.sg

This article was first published in Mind Your Body, The Straits Times.