Diabetes mellitus is a multisystem disease with both biochemical and anatomical consequences. Diabetes in pregnant women may be pregestational, where diabetes (type 1 or type 2) is diagnosed before pregnancy, or gestational, which refers to diabetes diagnosed during pregnancy. While planning the management of risk pregnancies, including those complicated by diabetes, two vital questions should be asked: "How will this disorder affect gestational outcome?", and "How will pregnancy affect maternal clinical status?" Diabetes is associated with the most adverse fetal outcome, increased rates of miscarriage, congenital malformations, intrauterine fetal death, macrosomia, prematurity, and neonatal metabolic and respiratory disorders. In addition, the physiological changes associated with pregnancy can adversely impact maternal health. Retinopathy, nephropathy, neuropathy, hypertension/preeclampsia, and cardiovascular disease can all affect and be affected by pregnancy. I hope that this book will provide a comprehensive review of diabetes in pregnancy along with its complications and management, and that you will be able to apply this information to your professional practice.