Background. To assess the benefits and harm of dietary and lifestyle interventions during pregnancy to improve maternal and infant outcomes for pregnant women who are overweight or obese. Methods. Randomized controlled trials comparing any form of dietary or lifestyle intervention during pregnancy for women who are overweight or obese with no treatment to improve maternal and infant health were considered. The Cochrane Controlled Trials Register (CENTRAL), PUBMED and the Australian and International Clinical Trials Registry were searched (date of last search November 2007). Results. Two published trials were identified with no statistically significant differences identified between the intervention and standard care groups for maternal or infant health outcomes. Conclusion. There is limited information available assessing the benefits and harm associated with dietary and lifestyle interventions for overweight and obese pregnant women. Further evaluation through randomized trials with adequate power is required.