Gestational diabetes mellitus (GDM) is high blood glucose (hyperglycemia) first occurring or first recognised during pregnancy. Between 1% and 14% of pregnant women develop GDM, with some at a higher risk than others (for example, women who are overweight or obese, older, of particular ethnicities, have had GDM previously, or have a family history of type II diabetes). GDM can cause significant health problems for mothers and babies. The babies may grow very large and, as a result, be injured at birth, or cause injury to mothers during birth. Women with GDM have an increased risk of having an induced birth, of their babies being born bycaesarean section, and of having a preterm birth (before 37 weeks of pregnancy). Additionally, there can be long-term health problems for mothers and babies, including an increased risk of type II diabetes. Some diets (for example, those with low fibre and high glycaemic load) and physical inactivity, are potentially modifiablerisk factors for GDM. There is evidence that lifestyle interventions in the generalpopulation (promoting diet and exercise changes) can prevent type II diabetes, and it has been suggested that these interventions may help prevent GDM in pregnancy.
This review assessed the effects of combined diet and exercise interventions for preventing GDM. We identified 13 randomized controlled trials (involving 4983 women and their babies). The studies were of moderate quality. Women who received diet and exercise interventions were compared with those who received nointervention. No clear differences between the two groups of women were seen in the risks of GDM, caesarean birth, or large-for-gestational age babies. Only one trialreported on deaths of the babies around the time of birth and did not show any difference between groups. Babies born to mothers receiving diet and exercise interventions were less likely to be born preterm, and some women who received the interventions improved their diet and physical activity. Very few other differences were shown between groups. The trials varied in their risk of bias, and also the interventions they evaluated. None of the trials reported on costs of health care, or long-term health of the mothers and babies.