Gestational diabetes mellitus is one of the major medical complications of pregnancy. Untreated, the mother and the unborn child may experience morbidity and fetal death may even occur. It is important to diagnose and treat all hyperglycaemia appearing during pregnancy. Ideally, a screening and diagnostic test that identified all women at risk for hyperglycaemia-associated complications would be employed in all pregnant women. Unfortunately, there is no such test available currently. The best alternative is to administer an oral glucose challenge test to all pregnant women and then apply the best strategies for interpretation. This article discusses the limitations of our present diagnostic tools and suggests an option for the clinician until the definitive test has been elucidated. In addition, this article outlines one dietary and management strategy that has been associated with an outcome of pregnancy that is similar to the outcome of pregnancies in healthy women. This strategy includes starting with a 'euglycaemic' diet (comprising <40% carbohydrates and greater than or equal to40% fat), which can then be individualised according to the patient's glucose levels. Appropriate exercise, such as arm ergometer training, may enhance the benefits of diet control. For patients who require insulin, if the fasting glucose level is >90 mg/dL or 5 mmol/L (whole blood capillary) then NPH insulin (insulin suspension isophane) should be given before bed, beginning with dosages of 0.2 U/kg/day. If the postprandial glucose level is elevated, pre-meal rapid-acting insulin should be prescribed, beginning with a dose of 1U per 10g of carbohydrates in the meal. If both the fasting and postprandial glucose levels are elevated, or if a woman's postprandial glucose levels can only be blunted if starvation ketosis occurs, a four-injections-per-day regimen should be prescribed. The latter can be based on combinations of NPH insulin and regular human insulin, timed to provide basal and meal-related insulin boluses. The total daily insulin dose for the four-injection regimen should be adjusted according to pregnant bodyweight and gestational week (0.7-1 U/kg/day); doses may need to be increased for the morbidly obese or when there is twin gestation. There is now some evidence that insulin lispro, other insulin analogues and oral anti hyperglycaemic drugs may be beneficial in gestational diabetes, and more data on these agents are awaited with interest.
