Should I keep training when pregnant?

Pregnant? Training doesn’t have to stop once you've a 'baby on board’, says Dr Catherine Spencer-Smith. In fact, it’s best to keep training. Here she shows you how…


Years ago, doctors encouraged women to do nothing more than put their feet up for the whole nine months of their pregnancy. These days we know better, and many women safely continue running, and enjoying it, while growing a baby.


Pregnant mums who keep fit are less likely to experience back pain; tend to gain less weight; are less likely to need an operative delivery (Caesarean section); lose the weight quicker; and are less likely to suffer from post-natal depression than sedentary mums.

Additionally, the cardiovascular changes needed to cope with having to pump blood around the placenta and womb may mean some women return to training after birth fitter than ever.

But not all would-be mums should train during conception and pregnancy, and it’s very important that you discuss your plans with your GP, midwife and obstetrician.

To train during pregnancy, you should already be an established runner (in other words, used to running at least three times a week for the last six months).

Also, if you have irregular periods or a history of recurrent miscarriages, you may be advised not to train because of possible conception issues.

Once pregnant, if you’ve been found to have a condition called placenta praevia (a very low-lying placenta), or if you develop blood-pressure problems, you should avoid most forms of training.

If you’ve been given the green light to train, you now need to be aware of the potential risks.

Can running while pregnant hurt the baby?

Although it’s never been formally tested in humans, animal studies have shown that running at intense levels for long periods of time (1-2hrs) can cause problems with the developing foetus due to temperature increases within the womb.

In essence, this means that to enjoy safe running, you must train at low intensities and keep cool.

It’s advisable to train wearing a heart-rate monitor and to keep your heart rate below a ceiling of 140bpm. You should train outdoors and ensure you keep hydrated by drinking 100ml of fluid every 15mins.

This is particularly important during the first 14 weeks of pregnancy. Consider training on an outdoor track so that, if you stop, you won’t be stranded. You’ll also always be near a loo.

Your training sessions should be gentle – now is not the time for speed work, fartlek sessions or races.

You should consider reducing training sessions to every other day if you’re used to training five or six days a week, to ensure that you get plenty of rest.

How does your body change in pregnancy and how does that affect your ability to train?

Some women find they’re too nauseous to run in the first trimester (first three months) and their running is hampered by frequent trips to the loo. It’s important to get in the habit of practising pelvic-floor exercises, to help you avoid bladder accidents – ask your midwife for advice.

Some women will begin to feel better by the time they’re into the second trimester. At this stage, the baby and womb will increase in size and will gradually begin to shift the body’s centre of gravity forwards.

As a result, there tends to be a compensatory lordosis (or increase in the arch in the small of the back). This can lead to back pain or feeling off-balance or clumsy, so avoid off-road running.

Meanwhile, breast enlargement brings other challenges like tenderness and top heaviness.

The body has to prepare to pass a baby through its pelvis, and so it produces a hormone called relaxin. This literally relaxes soft tissue structures such as ligaments and tendons.

You may feel that your pelvis is shifting around and the body is potentially more prone to injury, so go careful.

If at any stage in the pregnancy you experience breathlessness, light-headedness, visual changes, or blood or fluid loss from the vagina, it’s imperative you stop training immediately and seek medical attention.

Finally, pregnancy can cause your feet to swell and your changing biomechanics may well be reflected in your running action. You should have your footwear assessed in a specialist running shop, as many need a more cushioned, or motion-controlling, shoe.

Your running wardrobe will need adaptations to accommodate the bump. Choose gear that enables you to stay cool and get a well-fitting sports bra. Don’t be surprised if you need to obtain bras in different sizes as the pregnancy progresses.

Is it safe to cycle when pregnant?

Falling off is a major fear for expectant mums. In reality, this doesn’t pose a big problem provided you use common sense. Stick to quiet roads and avoid hills.

Babies are robust and well protected by amniotic fluid, so tumbles only tend to affect the pregnancy if the mother is seriously injured.

Use a heart-rate monitor to keep under 140bpm, keep cool and avoid cycling in hot weather. Ensure you stay hydrated and remember: as your tummy grows, your centre of gravity will change, so avoid riding in big groups if there are tricky stops and turns.

You may want to change to a more upright bike – raising your stem about 5mm per week and tilting your saddle forwards should help.

Is it safe to swim when pregnant?

Swimming is ideal exercise for pregnancy and there’s no evidence that swimming in clean pools poses a risk to mum or baby. The only women who shouldn’t be swimming are those who’ve had problems with cervical incompetence (weak neck of the womb), early rupture of membranes or problems with a very low-lying placenta.

Diving and tumble turns are best avoided. Later in pregnancy, swimming on your back isn’t a good idea due to the pressure of the baby on mum’s major blood vessels in the abdomen.

Once again, remain below a ceiling of 140bpm and it’s very important to keep cool. Sitting in the hot tub or sauna is a big no-no.

Getting in and out of the pool becomes trickier as your tummy expands, so use the steps rather than scrabbling out over the side. And for obvious safety reasons, you should avoid open-water swimming.

When should you stop exercising when pregnant?

It would be a heroic woman who continued running during the last three months of pregnancy. Here the baby competes for space with the bladder, bowels and diaphragm.

Shortness of breath, indigestion, backache and swollen ankles are commonplace, and you may prefer to walk briskly instead. Having said that, plenty of athletes continue to train right up until the time of delivery, and you should be guided by how you feel.

What should you eat during pregnancy?

It’s important to consider what you’re eating during your pregnancy and training. It’s a myth that you need to ‘eat for two’ and, overall, the pregnancy probably only requires around 200-300kcal extra per day.

Every woman should be taking a folic acid supplement, before and during the first three months. Eat a diet rich in iron because anaemia can be a problem, and make sure you get enough calcium for the developing baby.

You may find that smaller, more frequent meals induce less heartburn, and it’s vital to keep yourself hydrated.

How quickly can you return to exercising after giving birth?

What happens to your training after the event will depend on your delivery. If you had a ‘normal’ delivery (either vaginal or operative), it’s okay to start gentle, walking-type exercise after a week.

It’s a really a good idea to go for a ‘Mummy MOT’ with a specialist women’s health physio. This is typically a check-up at about six weeks, and the physio will take you through a pelvic floor strength and tummy gap assessment and they will tailor an exercise programme to help you tune things up.

Pilates post-pregnancy is a great way to ensure your pelvic floor, core and back are in a robust condition to tolerate getting back into running. As a guide, running should probably wait until six weeks after the birth, and up to 12 weeks if you’ve had a Caesarean.

If breastfeeding, feed the baby before you run (some babies may be fussy about the effect lactic acid has on the milk’s taste).

You could bring your baby running with you by pushing a baby jogger. If you do this, the baby must be at least 16 weeks old.


Pregnancy is an exciting time and you should be able to continue enjoying exercise provided you’ve checked with your doctor or midwife. Forget about racing. Concentrate on keeping in good shape – you’ll reap the benefits once your baby is delivered.