DM (hyperglycemia secondary to either insulin deficiency or relative insulin insensitivity) is a significant medical condition with a potentially profound impact on pregnancy. Uncontrolled diabetes prior to or early in the course of pregnancy is associated with a variety of birth defects, including renal, gastrointestinal, cardiac, central nervous system, and skeletal abnormalities. The presence of diabetes may alter the interpretation of some prenatal tests including α-fetoprotein and obstetric triple screen. Pregnancy may, in turn, affect the course of diabetes, worsening glucose control in patients with pre-existing diabetes.