Exercise during pregnancy

With the start of the London 2012 Olympics less than a year away, athletes such as Paula Radcliffe and the Canadian heptathlete, Jessica Zelinka, remind us that it is possible not only to return to world class competition after having a baby but also to continue training—albeit with some modifications—throughout pregnancy. The prevalence of obesity is increasing: in 2007, 24% of women in the United Kingdom aged 16 and over were obese compared with only 16% in 1993. One of the aims of the London 2012 Olympic bid was to encourage the whole population to become more physically active. This should include pregnant women too.

Recognising the beneficial effects of exercise during pregnancy is not new. In 1900, J M Ballantyne, who helped pioneer antenatal care—or as he put it pre-maternity care—in Edinburgh, designed a card to make sure essential advice during pregnancy was remembered and recorded by his pre-maternity nurses. This included a tick box regarding exercise and rest.1 In 1945, the textbook Williams Obstetrics advised 30 minutes of exercise twice a day.

Recent recommendations suggest that, in the absence of medical or obstetric complications, either 30 minutes or more of moderate exercise a day on most, if not all, days of the week,2 or 30 minutes of moderate intensity activity a day,3 should be the targets in pregnancy. This recommendation slightly exceeds but is not dissimilar to the most recent advice to UK adults of at least 150 minutes of activity a week.4 Not all women achieve these levels of activity before pregnancy, and activity often decreases during pregnancy.5 6 The amount of exercise performed is often proportional to the woman’s concerns about safety.7

Both the Royal College of Obstetricians and Gynaecologists and American College of Obstetricians and Gynecologists have excellent patient information leaflets that cover which types of exercise are recommended in pregnancy and which should be avoided.8 9 Precise guidance is given on the level of exertion and relevant precautions. Exercise in pregnancy has the same beneficial health outcomes as in non-pregnant women. It also relieves many of the minor ailments of pregnancy, such as tiredness, leg oedema, back pain, constipation, and nausea. It does not increase the risk of miscarriage and can help prevent and control gestational diabetes. Exercise also helps prevent excessive weight gain in pregnancy, and women who exercise during pregnancy are more likely to exercise after the birth and therefore lose the weight gained during pregnancy. Return to pre-pregnancy weight between pregnancies helps reduce the risk of obesity later in life.

There seems no doubt that moderate intensity exercise during pregnancy is safe for uncomplicated pregnancies, but there is continuing debate about vigorous and longer periods of exercise. A study in a Danish cohort of 85 139 pregnant women found a significant link between high levels of exercise in early pregnancy (>270 minutes a week) and the risk of severe pre-eclampsia, although the absolute risk was still low at 1.1-1.3%. There was no link between exercise at the currently recommended levels (210 minutes a week) and severe pre-eclampsia.10

There is also increasing interest in measuring the effects of maternal exercise on the fetus.11 The effect of maternal exercise on birth weight is not consistent between studies. Obese women and women who gain excessive weight during pregnancy have bigger babies. If maternal exercise results in a small reduction in birth weight in babies in the high end of normal or large for gestational age range, childhood obesity may be reduced and the risk of metabolic disease in later life lessened, consistent with the Barker hypothesis.11 More research is also needed about the effects of exercise on overweight and obese women because many studies were conducted on normal weight women or women who were already physically active before pregnancy.12

Since the advent of antenatal care in the early 1900s, the list of advice and tests that need to be discussed during this important period of a woman’s life has increased greatly. Discussions about the amount and type of exercise that is recommended during pregnancy may be seen as less important than screening for Down’s syndrome or deciding whether or not to screen for gestational diabetes. But the beneficial effects of exercise during pregnancy to both the mother and developing baby need to be emphasised, and women need reassurance that they are doing no harm as long as their pregnancies are progressing normally. The challenge for the future will be to encourage all women with uncomplicated pregnancies to attain at least the currently recommended exercise levels while continuing to research what type, what intensity, and how much exercise in pregnancy will give the best maternal and fetal outcomes.