Dietary advice in pregnancy for preventing gestational diabetes mellitus

Tieu J, Crowther CA, Middleton P

Summary

Dietary advice during pregnancy to prevent gestational diabetes

Diabetes mellitus is associated with abnormal glucose metabolism, with raised blood sugar and sugar in the urine. When this arises in pregnancy and disappears after birth, it is called 'gestational diabetes mellitus' or GDM. Between 1% and 14% of women develop GDM in pregnancy, with some women more at risk than others, and the severity can vary too. Risk factors for gestational glucose intolerance include being of a particular ethnicity, previous GDM, family history of type II diabetes mellitus and being older. Often there are no symptoms, or the symptoms can include tiredness, excessive thirst, passing a lot of urine and blurred vision. GDM can also cause significant problems such as a very large baby, an increased risk of the shoulder getting stuck during birth and injury to the mother during birth. There is also an increased chance of having an induced birth and caesarean birth. Babies can also often be born too early and have less chance of surviving, have problems with breathing and jaundice. In addition, there can be long-term effects such as increasing the risk of diabetes for mother and child later in life. Diet may play a significant part in the control of diabetes, with wholegrain carbohydrates and low glycaemic index diets (LGI) being helpful. LGI diets aim to slow down the digestion of food, allowing the body to better adjust to the load of sugar coming in after a meal. It is possible, therefore, that dietary advice in pregnancy may reduce the number of women who get GDM and its effects.

The review of dietary advice in pregnancy to reduce GDM identified three trials involving 107 women, undertaken in Western countries. One trial involving 25 women looked at high-fibre diets compared with normal pregnancy diets. Two trials, involving 82 women, looked at LGI diet compared with high glycaemic index diet, with one of these trials also including an exercise component. The outcomes relevant to the review in the trial on high-fibre diets were inconclusive. The results on the low glycaemic index diet suggested that this may be beneficial to the mother and child. However, the evidence was not strong enough to be confident of these effects.