Diabetes mellitus complicates somewhere between 1 and 20% of all pregnancies worldwide. Women with all types of diabetes, including type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus, and gestational diabetes mellitus, as well as their infants, are at increased risk for a number of different complications. However, achieving and maintaining euglycemia throughout gestation has been demonstrated to reduce the risk of adverse outcome for both the mother and her offspring. Traditional management approaches use a combination of diet, exercise, intensive insulin regimens and multiple self monitored blood glucose determinations. There are a number of newer agents available to treat diabetes mellitus; however, their safety in pregnancy has not been thoroughly tested. Although the oral hypoglycaemic drugs are not customarily used during gestation in most of the US and Europe they have had considerable use in South Africa. Animal and human studies of the teratogenic effects of these drugs have yielded conflicting data and it is difficult to distinguish between the teratogenic effects of poor maternal metabolic control and the agents themselves. This article also addresses the current state of the knowledge regarding the drug safety of a variety of medications for conditions, including hypertension and preterm labour, commonly encountered in the management of the pregnant women with diabetes mellitus.