Diabetes mellitus is one of the most common maternal illnesses resulting in congenital malformations. All complications of pregnancy, either with diabetes pregestational or gestational, are directly or indirectly related to the degree of metabolic control. If it is not treated properly, diabetes in pregnancy causes major problems for both mother and fetus. The only way to reduce complications to the minimum and locate them near to those of the normal population, is to achieve a good metabolic control. Multi-disciplinary approach in which obstetricians, physicians, paediatricians are involved, combined with intensive monitoring and therapy throughout pregnancy, could achieve successful results in women with complicated diabetes. This objective is subordinate to early diagnosis for gestational diabetes and planning of pregnancy for diabetic women.