Dietary supplements may be used by pregnant women if they perceive them to be natural and healthy products, if they are fearful of using prescription drugs, or if they are recommended by a health care provider. Usage surveys indicate that midwives feel comfortable in recommending some herbal products to their patients. There are sufficient data from randomized controlled trials on omega-3 fatty acids and ginger that their pharmacologic properties, efficacy, and safety data for specific indications in maternal health can be evaluated. Requests for information regarding these substances are likely to be encountered by health care providers who care for pregnant women. Omega-3 fatty acids benefit gestation, infant vision, and neurodevelopment, while effects on major depression in pregnancy and postpartum depression are less clear. Ginger is efficacious for nausea and vomiting in pregnancy but is limited in its safety data. Pharmacologic properties of each supplement and pathophysiology related to each indication are reviewed. It is recommended that pregnant and lactating women be advised to take an omega-3 fatty acid supplement daily, while the recommendation to use ginger is tentative and will likely be based on each practitioner's comfort level with the safety data that are presented.