Why exercise during pregnancy?

Pregnancy exercise can reduce tiredness, back pain and weight gain, as well as the risk of unplanned caesarean and gestational diabetes. For babies, exercise during pregnancy can improve a baby’s heart rate health, birth weight and brain maturity, so it’s important to encourage mothers to stay active^1-3.

For both mother and baby, there are a multitude of benefits to exercising during pregnancy:

Potential benefits for mother

• Reduced lower back pain⁵, pregnancy constipation¹² and tiredness¹³
• 30% less likely to develop gestational diabetes⁶
• Less likely to need an unplanned caesarean^7,8
• Experience fewer incidences⁵ and reduced severity¹⁰ of depression
• Gain less weight during pregnancy⁸
• Are less likely to develop urinary incontinence¹¹
• Have reduced incidents of pregnancy constipation¹²
• Less pregnancy tiredness¹³
• May have shorter labour⁵

Potential benefits for baby

• Develop a healthier heart with a lower resting heart rate after birth¹⁵
• Be born at what is considered a ‘normal’ birth weight, rather than overweight¹⁶
• Be born with more mature brains and are quicker to develop neurologically¹⁷
• Experience a reduced risk of respiratory distress at birth (if born to high-risk mothers)¹⁸
• Less maternal stress could reduce impact on immune system development¹⁹

Exercising safely during pregnancy

There are a number of activities designed specifically for expectant mums, like pregnancy yoga. But if the mother loves to run, swim or go to the gym, they should be able, and encouraged, to continue their usual routine with a few modifications. Some days the mother may feel more energetic than others, so they should always be told to take things at their own pace.

Healthcare professionals should encourage expectant mothers to do the following exercises:

• Running or brisk walking is free and can be done anywhere, anytime. Even a gentle jog or a walk with the dog can raise the heart rate enough to be beneficial for expectant mothers.
• Swimming while pregnant is relaxing for the mind and low impact on the body. Most swimming strokes are safe²⁰, including backstroke – although those with symphysis pubis dysfunction (SPD) may want to avoid the breaststroke²². Some local councils offer free or discounted sessions for expectant mothers.
• Strength training, using moderate rather than heavy weights, is normally safe to continue with if weights are part of a usual exercise routine – but it may be necessary to make a few modifications.
• Yoga and pregnancy yoga can be good methods of aiding relaxation, which also have the benefit of retaining strength and flexibility.

Pelvic floor exercises in pregnancy

The pelvic floor plays a particularly important role during pregnancy and labour^22,23. Initially, it supports the weight of the growing baby. Later on, when labour begins, the pelvic floor helps to rotate the baby’s head into the ideal position, ready for birth. As the womb contracts to push the baby down, the gentle resistance from the flexible pelvic floor below encourages the baby’s chin to tuck and their head to turn. Once in this position, it is easier for the baby’s head to pass under the pubic bone, ready for crowning²⁴.

A new mother’s pelvic floor may be understandably weaker after birth. Around 40 percent of women who have given birth experience ‘stress incontinence’ – leaking urine when they sneeze or cough²⁵. Mothers can experience stress incontinence regardless of delivery method, and it is thought to be mostly a consequence of being pregnant in general²⁶. However, pregnant women undertaking pelvic floor muscle training have been found to have a lower incidence of urinary incontinence²⁷ after birth.

How to help pregnant mothers strengthen their pelvic floor

With regular, simple exercises, the pelvic floor muscles can be strengthened in order to reduce the likelihood of certain problems later on²⁸. The most effective way to improve the strength and stamina of pelvic floor muscles is to encourage expectant mothers to combine both short and long squeezes.

Here are a few simple exercises to help strengthen a pregnant woman’s pelvic floor:

• First, lift up and squeeze the back passage as if trying to hold in a bowel movement. Then lift up and hold the muscles of the vagina and bladder, as if holding in urine.
• For short squeezes, hold for a second or two, then release. Rest for one or two seconds before squeezing back and front again.
• For long squeezes, hold for at least four seconds, then release. Rest for a few seconds, then repeat. Over time, try to work up to holding the squeeze for 10 seconds.
• Do as many pelvic squeezes as possible, long and short, before the muscles get tired. Aim to repeat the exercises three times a day.

What should expectant mothers avoid whilst exercising during pregnancy?

Perhaps the simplest change expectant mothers have to make is avoiding lying flat on their backs for long periods of time, especially after 16 weeks. The weight of the bump pressing on certain blood vessels can reduce cardiac output²⁹, cause dizziness and affect the flow of blood that carries nutrients and oxygen to the baby. Instead, expectant mothers should be advised to lie on their sides.

While this means traditional stomach crunches should be avoided during exercise, core and pelvic floor strengthening exercises should still be included in their exercise routines. One way to work the core is for the mother to get onto all fours and make a box shape, with hands under the shoulders, knees under the hips, and a straight back. The stomach muscles should be pulled in, and the back arched towards the ceiling like a cat. This should be held for a few seconds, return to neutral, then repeat³⁰.

What is a ‘safe’ pregnancy heart rate?

In the past, experts have recommended that a pregnant woman’s heart rate should not exceed 140 bpm, but understanding of fitness has since progressed. An increase in resting heart rate (by approximately 10 bpm) is a normal physiological consequence of pregnancy³¹. Just like fitness levels, heart rates vary between individuals, so keeping the heart rate below a specific value is not appropriate. The best rule is for expectant mothers to exercise at a moderate intensity, in such a way that they are able to hold a conversation throughout.

What is a ‘safe’ body temperature?

Specific recommendations regarding body temperature during pregnancy are sparse; however, experts agree that expectant mothers should avoid undertaking activities that will raise their core temperature by more than 2°C – or above 38.9°C³². This is because such a temperature change may result in hyperthermia (the opposite of hypothermia). Hyperthermia during pregnancy has been linked to a twofold increase in the risk of birth defects impacting the spine or brain. As such it is not advisable to use hot tubs or spas during pregnancy, and hot yoga should be avoided³³.

However, moderate exercise – whether it’s running, swimming or regular yoga – should not raise the core temperature above these levels and should therefore be actively encouraged by healthcare professionals.

Which exercises should be avoided when pregnant?

Although not all of the following activities have been directly linked to harming the baby during pregnancy, certain activities may put expectant mothers in a position where falls or knocks to the unborn baby are more likely. Healthcare professionals should inform pregnant mothers that the following exercises should be avoided³⁴:

• Contact sports like martial arts, football, rugby, squash and hockey all carry a risk of impact.
• Horse riding, cycling, skiing and gymnastics can become more difficult as the baby grows and the centre of balance shifts. Expectant mothers should be advised to avoid these activities, and any others that carry a risk of falling.
• Scuba diving while pregnant should be avoided as the baby has no protection against decompression sickness (‘the bends’) or gas embolism – bubbles in the bloodstream that can cut off blood supply or cause breathing difficulties³⁵. In fact, scuba diving while pregnant has been directly linked to birth malformations³⁶.
• Bikram yoga (or hot yoga) involves a sequence of postures practised in a heated room. While no one has studied the effects of hot yoga specifically, experts agree that pregnant women should avoid raising their core body temperature to reduce the risk of neural tube defects.

IMPORTANT NOTICE: Breastfeeding is best for babies. Infant formula is suitable from birth when babies are not breastfed. Follow-on milk is only for babies over 6 months, as part of a mixed diet and should not be used as a breastmilk substitute before 6 months. We advise that all formula milks including the decision to start weaning should be made on the advice of a doctor, midwife, health visitor, public health nurse, dietitian, pharmacist or other professional responsible for maternal and child care. Foods for special medical purposes should only be used under medical supervision. May be suitable for use as the sole source of nutrition for infants from birth, and/or as part of a balanced diet from 6–12 months. Refer to label for details.