Exercise in pregnancy
Why exercise matters in pregnancy, which exercises are done and how, the physiological changes involved, what the studies show and when exercise is not advised.
As the uterus grows and body weight increases in pregnancy, posture changes — and that change in posture causes pain in the lower back and the back.
Why exercise in pregnancy
Exercise in pregnancy is done in order to:
- correct the postural changes that arise
- reduce back pain
- teach the breathing and relaxation needed during labour
- increase the elasticity and strength of the abdominal and perineal muscles
- prepare the mother psychologically for the birth
- allow her to contribute knowingly to the birth and so make it easier
When to start
An exercise programme should begin after the first three months and continue regularly, once a week, until delivery.
Who should set the programme
Every woman is different, psychologically and physically. Each pregnant woman should therefore be assessed by a physiotherapist and have her programme planned individually.
Which exercises are done before birth
- Breathing exercises: deep abdominal breathing, deep chest breathing, laryngeal breathing
- Relaxation exercises
- Exercises to reduce back and lower back pain
What they are for
Breathing exercises allow the mother to use her breath in a controlled way during the pains of the second stage of labour, so that she can push effectively. Relaxation exercises teach her how to relax during the pain-free phase, building the reserve of energy needed for the birth and helping her use her strength usefully.
Suitable positions for relaxation
- On the back: a thin pillow under the head, knees bent with a pillow beneath them, feet in a natural position.
- On the side: a pillow under the head, body turned forward, the lower arm straight alongside, legs slightly bent with a pillow between them. The upper arm can be supported on a pillow.
A woman who can relax will help the cervix open during the first stage of labour.
Exercises for back and lower back pain
- Pelvic tilt: lie on your back with knees bent and a thin pillow under the head; press your hand down into the bed, count to ten and relax. Do this sitting and standing as well.
- With the pelvic tilt, draw the knees towards the abdomen and straighten them. Breathe in as you straighten, out as you draw them in.
- Lying on your back with knees bent, raise the head to look towards the knees and lower it. Breathe in as you lower, out as you raise. Do this together with the pelvic tilt.
- In the same position, press the whole back into the bed, count to ten and relax.
- In the same position, squeeze the buttocks together, count to ten and relax.
- Lying on your back, cross the legs and repeat the previous exercise.
- On your back with knees bent, open the knees out to the sides until they touch the floor, then relax.
- On your back with knees bent, lower the legs to the right and then to the left. This can also be done one leg at a time.
- On hands and knees with a flat back: breathe out as you arch the back upwards and lower the head; breathe in as you flatten and hollow the back and raise the head.
- As the baby grows and weight increases, pain and circulatory problems can develop in the legs. To prevent this, lie on your back with the feet raised on a pillow, pull the foot up and down from the ankle, and make circles with the ankle.
- Sit cross-legged. Use your hands to press the knees gently towards the floor and release. Repeat with the soles of the feet together.
- With the feet 20 cm apart, turn the legs outwards from the hip, squat and stand.
- Stand in front of a mirror and correct your posture.
Everyday movement
- When doing housework, dusting or cleaning floors, work on your knees.
- To sit up from lying on your back, first turn onto your side, then push up using your arms.
- Rise from a chair by taking the weight through your legs and using support.
Movements to avoid
- sudden movements
- lifting heavy weights
- squatting to sit or to work in late pregnancy
How often
Each exercise should be repeated regularly, 5-6 times every day. Women who exercised before pregnancy can continue with the same programme, provided it is not strenuous.
Excessive weight gain in pregnancy, and failing to lose the extra weight within six months after the birth, leads to obesity in the long term. Exercise and balanced eating keep weight gain through pregnancy within the desired range. Exercise in pregnancy reduces the risk of gestational diabetes and of long-term obesity, and by improving posture, muscle tone, strength and endurance it lays the ground for a faster labour and a faster recovery. It also helps with back pain, wind and swelling in the feet — all common complaints. A pregnant woman who exercises should, however, take an additional 300 kcal a day.
How thinking has changed
Attitudes to exercise in pregnancy have shifted over the years. In 1985 ACOG recommended that aerobic exercise last no more than 15 minutes and that the heart rate not exceed 140 beats per minute. Ten years later, on the basis of physiological evidence, the same committee stated that women with uncomplicated pregnancies could exercise at the same level as women who were not pregnant.
Physiological effects and adaptation
Cardiovascular. Cardiac output rises by 50%, the heart rate is 15 beats faster than at rest, and blood volume increases by 45%. Increased venous capacity lowers blood pressure, the skin's vessels dilate, and the resulting heat loss reduces the tendency to overheat.
There were concerns that the increased blood flow to the muscles during exercise might mean less blood pumped to the uterus and placenta. But compensatory changes brought on by exercise — a rise in maternal haematocrit and in oxygen extraction — mean foetal oxygenation is not impaired. The foetal heart rate rises briefly by 5-15 beats, which does not place the foetus in danger. Episodes of foetal bradycardia are not seen in the absence of an obstetric or medical complication.
After the first trimester, however, the supine position should be avoided, since it reduces maternal cardiac output. Uterine blood flow has also been shown to be reduced in women living at altitude. Women living above 2,500 metres are advised to avoid excessive physical exertion until at least four to five days have passed.
Metabolic. A maternal core temperature above 39.2 °C is known to have possible teratogenic effects in the first trimester. Increased ventilation and skin blood flow are the adaptive changes that protect against overheating in pregnancy. Even so, to guard against it, adequate hydration is advised and exercising in very hot or humid environments is not.
Because of the limited expansion of the diaphragm in pregnancy and the increased oxygen requirement of the foetus, VO2 max during exercise is significantly lower than in a woman who is not pregnant. Carbohydrates are therefore used more heavily. In prolonged (over 45 minutes) or strenuous exercise, plasma glucose concentrations fall significantly. To reduce the risk of hypoglycaemia, adequate calorie intake during exercise is advised and the duration should be kept below 45 minutes.
Musculoskeletal. The changes in a pregnant woman's musculoskeletal system increase the risk of injury during exercise. Growth of the breasts, uterus and foetus increases the lumbar curve, pulls the centre of gravity forward and loads the lower back; hormonal changes make the joints looser and more mobile. For these reasons all exercise in pregnancy should be done without straining and without loading the joints heavily.
Effects on the baby
Birth weight. The findings on the birth weight of babies born to women who exercise are contradictory.
A study by Clapp in 1990 found that when pregnant women increased their exercise level by more than 50% compared with before conception, birth weight fell significantly. Another study, by Sternfeld, found no difference in birth weight between women exercising heavily and those with a sedentary lifestyle. In a prospective study of 800 pregnant women by Hatch and colleagues, women exercising at a level expending 2,000 kcal a week had babies of higher birth weight than women who did not exercise. In 1998 Pivarnik concluded: the evidence available at present indicates that moderate to vigorous physical activity during pregnancy may have positive effects on birth weight — though it should not be forgotten that heavy exercise programmes can lead to low birth weight.
Length of pregnancy. It was thought that the increased release of noradrenaline and prostaglandin during exercise might stimulate uterine activity and premature birth. Very little research exists on this. In a 1998 study, Hatch followed 876 pregnant women expending more than 1,000 kcal a week in aerobic activity and found a reduction in the risk of premature birth compared with a group doing no exercise — supporting the conclusion that exercise in pregnancy is safe.
Effects on the mother
Symptoms such as nausea, fatigue and back pain are reduced in women who exercise. An observational study of 398 pregnant women found an inverse association between exercise and symptoms.
Labour and delivery. The effect of exercise on labour is uncertain. Many women report feeling more energetic through exercise and finding the birth easier as a result. One poorly controlled, non-randomised study found labour to be shorter in women who exercised. A 1974 study by Pomerance found labour shortened in multiparous women who exercised, though the effect was not seen in first-time mothers. Many other studies have found no correlation between level of exercise and length of labour.
Exercise and gestational diabetes
The American Diabetes Association recommends exercise as a useful adjunct where normal blood glucose cannot be achieved through diet alone in gestational diabetes. A randomised study by Jovanovic in 1989 compared patients following diet alone with those doing aerobic arm exercise. At the end of six weeks, HbA1c, fasting blood glucose and post-meal blood glucose had all fallen in the exercising group, with no improvement in the controls. In a further study by Bung and colleagues in 1991, a more intensive programme achieved normal blood glucose within a week.
General advice
Pregnant women who were previously sedentary should be encouraged to begin exercising. Starting with low-injury-risk activities such as walking or swimming, for no more than 20-30 minutes a day, can be recommended. Women who were already exercising are advised to continue with the same programme.
Points to watch during exercise:
- the programme should be regular
- stop exercising if signs of oxygen shortage develop — extreme fatigue, dizziness, air hunger
- exercise in a cool environment and avoid dehydration, so as not to overheat
- avoid prolonged exercise in the supine position in the second and third trimesters
- avoid contact sports and diving
- always take the calories the exercise requires (on average 300 kcal a day)
When exercise is not advised
The contraindications set out by ACOG in 1994:
- restricted growth of the baby in the womb
- persistent vaginal bleeding
- suspected cervical insufficiency, or a cerclage in place
- risk factors for preterm birth
- ruptured membranes
- pregnancy-induced hypertension
- serious chronic medical conditions