Context: Interventions targeting maternal obesity are a healthcare and public health priority. Objective: The objective of this review was to evaluate the adequacy and effectiveness of the methodological designs implemented in dietary intervention trials for obesity in pregnancy. Data Sources: A systematic review of the literature, consistent with PRISMA guidelines, was performed as part of the International Weight Management in Pregnancy collaboration. Study Selection: Thirteen randomized controlled trials, which aimed to modify diet and physical activity in overweight and obese pregnant women, were identified. Data Synthesis: There was significant variability in the content, delivery, and dietary assessment methods of the dietary interventions examined. A number of studies demonstrated improved dietary behavior in response to diet and/or lifestyle interventions. Nine studies reduced gestational weight gain. Conclusion: This review reveals large methodological variability in dietary interventions to control gestational weight gain and improve clinical outcomes in overweight and obese pregnant women. This lack of consensus limits the ability to develop clinical guidelines and apply the evidence in clinical practice.