The numbers of women of childbearing age with pregestational diabetes mellitus (diabetes existing before pregnancy) are increasing, primarily because more patients are developing type 2 diabetes at younger ages. The teratogenicity associated with hyperglycemia in early pregnancy is well documented, and tight glucose control minimizes the risk of congenital malformation. Preconception planning is essential; thus contraception that does not worsen complications of diabetes is desirable. In addition, because contraceptives are not 100% effective, the treatment of elevated blood glucose levels, hypertension, and dyslipidemia in these women requires consideration of unplanned pregnancy. We summarized the literature to aid clinicians in choosing individualized treatment that minimizes risk in case pregnancy occurs and maximizes benefit in preventing the complications of diabetes. In women with well-controlled diabetes without vascular disease, all contraceptive methods are safe. Intrauterine devices are recommended due to their minimal effects on risk factors for diabetic complications and their lack of reliance on patient adherence for efficacy. Among insulins, the insulin analogs-insulin lispro, insulin aspart, and insulin detemir-offer patients greater convenience than regular insulin and NPH insulin, and they are safe in case of unplanned pregnancy. Of the noninsulin agents, glyburide and metformin are the safest during pregnancy, but many of the other agents pose minimal risk as long as they are withdrawn during early pregnancy. The risks and benefits of angiotensin-converting enzyme inhibitors in women with compelling indications must be weighed individually. In hypertensive patients at a high risk for unplanned pregnancy, nifedipine should be considered due to literature supporting its safety during early pregnancy. Pravastatin is recommended for women with dyslipidemia who are using effective contraception because there have been no reports of birth defects with this statin when used during early pregnancy in humans and animals.