Appropriate preconception health care improves pregnancy outcomes. When started at least one month before conception, folic acid supplements can prevent neural tube defects. Targeted genetic screening and counseling should be offered on the basis of age, ethnic background, or family history. Before conception, women should be screened for human immunodeficiency virus and syphilis infection and begin treatment to prevent the transmission of disease to the fetus. Immunizations against hepatitis B, rubella, and varicella should be completed, if needed. Women should be counseled on ways to prevent infection with toxoplasmosis, cytomegalovirus, and parvovirus B19. Environmental toxins such as cigarette smoke, alcohol, and street drugs, and chemicals such as solvents and pesticides should be avoided. In women with diabetes, it is important to optimize disease control through intensive management before pregnancy. Medications for hypertension, epilepsy, thromboembolism, depression, and anxiety should be reviewed and changed, if necessary, before the patient becomes pregnant. Counseling about exercise, obesity, nutritional deficiencies, and the overuse of vitamins A and D is beneficial. Physicians may also choose to discuss occupational and financial issues related to pregnancy and to screen patients for domestic violence.