This protocol describes a two-armed RCT to evaluate the feasibility of an mHealth intervention to promote healthy nutrition, physical activity and weight gain in pregnant women who are overweight or obese prior to pregnancy. The protocol is guided by the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT), 2013 statement [35] and the Consolidated Standards of Research Trials (CONSORT) - EHEALTH guidelines [36,37]. An additional file shows the SPIRIT checklist (see Additional file 1).