5.4 Gestational diabetes
Gestational diabetes is diabetes that develops during pregnancy. There are no internationally agreed threshold blood glucose levels used to diagnose gestational diabetes. However, there is a trend towards using the IGT (impaired glucose tolerance) test criteria (see Section 4). Studies are ongoing to decide what threshold level is important in pregnancy. The increased metabolic demands imposed by pregnancy may just be enough to make a person predisposed to diabetes to ‘tip over’ into the condition. The diabetes commonly resolves after the baby is delivered, but a few mothers will have had undiagnosed Type 2 diabetes or have developed coincidental Type 1 diabetes. Having had a diagnosis of gestational diabetes, a woman is likely to develop diabetes in future pregnancies and is also more likely subsequently to develop Type 2 diabetes. Lifestyle advice should be given. A change of lifestyle, through increasing exercise and weight reduction, has been clearly shown to delay the development of Type 2 diabetes in those with IGT. During the pregnancy, the woman should be treated for diabetes by changes to her diet and exercise with or without insulin.
Case study 6 describes a person with gestational diabetes. It also introduces the idea of risk, which is discussed in Section 6.
Case study 6
Mrs Shah, aged 38 years, is 28 weeks into her fourth pregnancy. During her third pregnancy she developed gestational diabetes. She needed insulin to control her blood glucose level along with a change in diet. After the pregnancy she was very worried about developing diabetes as both her parents had had diabetes. She continued on her new diet. She now weighs 75 kg compared with 110 kg at the same stage during her last pregnancy. She has just had an oral glucose tolerance test for diabetes. The test was normal and she is delighted.
As previously mentioned, a family history of diabetes increases the risk of a person developing diabetes. Asians and some other groups such as African–Caribbeans have an increased risk of developing diabetes compared with Caucasians. Being overweight would increase this risk further. Mrs Shah has done what she can to decrease her chances of developing diabetes. Weight reduction and exercise have been shown in several studies to reduce the risk of developing diabetes and she would have been advised at the end of her third pregnancy to adopt a healthier lifestyle.