In 2010, marathon world-record holder Paula Radcliffe finished a 10 km charity run while 7 months pregnant. In 2011, Amber Miller completed the Chicago Marathon in 6 hours 25 minutes, and 7 hours later gave birth to a baby girl. Successful birth plans are not dependent on such feats of athleticism, but the exploits of Radcliffe and Miller raise the question: ‘Is it necessary—or safe—to exercise during pregnancy?’ As Blaize et al (2015: 198) suggest, women may not only fail to ‘reach the recommendations for exercising during pregnancy because of feelings of discomfort, fatigue, illness, and lack of enjoyment’, they may also consider it more important to relax during pregnancy than to exercise. Indeed, Barakat et al (2015: 2) suggest that past recommendations for exercise during pregnancy were ‘based more on social and cultural notions or “common sense” than any hard scientific evidence’.
But scientific evidence is emerging. When Noakes (2003) considered whether babies born to women who exercised during pregnancy weighed less and were at increased risk of abnormalities, he found clear evidence that children born to women who exercised during pregnancy were of normal weight and did not show increased risk of birth abnormalities.
In their review, Barakat et al (2015) concluded that healthy pregnant women, in the absence of obstetric complications, are able to cope with the physiological demands of moderate exercise. The authors state that moderate exercise is not a risk factor for either fetal or maternal pregnancy outcomes, and that health professionals may recommend a supervised programme of moderate exercise during pregnancy.
They also cited studies demonstrating that exercise during pregnancy improves depression-related symptoms, and that ‘the cardio respiratory response to acute exercise in pregnant women who were physically active throughout pregnancy was better than in women who remained inactive during gestation’ (Barakat et al, 2015: 3).
But what about exercise for women with gestational diabetes mellitus (GDM)? Most pregnant women are offered a maternal glucose screen (MGS) test to check for GDM, a high blood-sugar condition that can complicate 4–12% of pregnancies. Barakat et al (2012) note that the developed world is seeing an increased incidence of GDM, in line with the rise in obesity. In addition, recent evidence shows that expectant mothers who gain weight early in pregnancy may be at increased risk of GDM. Physical activity is one way to help break the pattern of GDM, childhood obesity and adult diabetes.
Barakat et al (2012) hypothesised that regular aerobic exercise during pregnancy would lead to improved MGS results, reduce maternal weight gain and result in fewer cases of GDM. They selected 83 healthy pregnant women, allocating 40 to an exercise group and 43 to a control group. The exercise programme lasted for 35–45 minutes (two land-based sessions and one aquatic session) three times a week throughout pregnancy. The results showed that MGS values in the exercise group were better than those in the control group. There were three cases of GDM in the control group but none in the exercise group. The authors concluded that a moderate physical activity programme during pregnancy improves levels of maternal glucose tolerance.
Although exercise is essential for glucose metabolic control and may prevent GDM, the type, duration and intensity of exercise during pregnancy to prevent GDM are not fully defined. This was addressed in a joint Spanish–Canadian study in which researchers investigated the effects of a combined exercise programme on land and water that used aerobic and muscle-toning activities (Cordero et al, 2015). A total of 257 pregnant women from Spain, all 10–12 weeks pregnant and with an average age of 33 years, were allocated to two groups. The intervention group of 101 women exercised for 60 minutes on land and 50 minutes in water, three times a week. The control group of 156 women received standard care. Each land session included aerobics, resistance exercises, pelvic floor exercises and stretching. Each aquatic session included swimming laps, step climbs, lunges and strength exercises in the water, and stretching. All sessions were supervised by a qualified fitness instructor.
The prevalence of GDM in the exercising group was 1%, compared to a prevalence of 8.8% in the control group. The researchers cite studies reporting that physical exercise reduced the prevalence of GDM in women. However, they also refer to one investigation which began an exercise trial with women at 18–22 weeks pregnant and found no difference between the exercising and non-exercising groups. They suggest, therefore, that early exercise intervention may be the key to GDM prevention.
Blaize et al (2015) highlight research establishing a link between infant low birth weight and type 2 diabetes mellitus (T2DB) in later life, and suggest that exercise during pregnancy reduces the risk of offspring developing T2DB. They report that maternal voluntary exercise in mice fed a normal diet positively influenced offspring's glucose and insulin tolerance during adulthood.
Making time for moderate physical exercise is an important factor to bear in mind when pregnant women juggle the competing demands of life.