Should gym-going stop for women who are pregnant? The quick answer is no, but there are serious questions to consider about the optimum type, frequency and intensity of exercise to keep mum fit and baby healthy. Women who exercise in pregnancy often feel more physically prepared for the birth and tend to recover more quickly after it. Here are some simple safety rules:

Don't overheat Getting too hot may cause swelling, raised blood pressure and dehydration. This doesn't mean that you can't sweat: you should during exercise. It simply means that you should avoid exercising in hot conditions, avoid wearing too much clothing and control your intensity levels.

Keep your heart rate controlled Imagine a scale of 1-10, with 10 being totally exhausted: you should not be rising beyond 7, at which point you will be breathing harder, getting warm, starting to sweat, but can talk comfortably. If you have a heart-rate monitor, you should keep your rate below 145 bpm. Swimming is good for limiting your intensity level, as the effect of water pressure on the body lowers the heart rate, while the water temperature has a cooling effect.

Limit high-impact exercises My general advice is to not jog, particularly in the second and third trimesters. But for some avowed joggers, a break from their favourite exercise is distressing, so this should be borne in mind when making your decision. Tennis can be adapted, while more intensive activities such as squash are probably too vigorous.

Short stretches only Stretching stiff muscles in your back, shoulders and legs is important, but do not hold a stretch for too long. Pregnant bodies produce a hormone, relaxin, which softens tissues around the pelvis to prepare it for birth. The hormone's wider effect means that prolonged stretching can induce hypermobility around joints, which can be painful and damaging. Limit your stretch time to only six or seven seconds per stretch hold.

Keep your blood pressure low Avoid exercises with large weights, particularly for the lower body. You are perfectly OK doing exercises such as squats and lunges without weights. These should be part of your routine. Try to exercise three or four days a week for 30-45 minutes each time during your first and second trimesters. During the third trimester, change your routine to shorter ones of 20-25 minutes long, four or five days per week. This will reduce your chances of becoming overtired.

www.mattroberts.co.uk

Times recommends

• Are eldest children really a cut above?
• Peaches Geldof: censored
• Top 10 style-setting films of all time