Objective: Gaining too much or too little weight in pregnancy (according to Institute of Medicine (IOM) guidelines) negatively affects both mother and child, but many women find it difficult to manage their gestational weight gain (GWG). Here we describe the use of the intervention mapping protocol to design ‘Come On!’, an intervention to promote adequate GWG among healthy pregnant women.

Design: We used the six steps of intervention mapping: (i) needs assessment; (ii) formulation of change objectives; (iii) selection of theory-based methods and practical strategies; (iv) development of the intervention programme; (v) development of an adoption and implementation plan; and (vi) development of an evaluation plan. A consortium of users and related professionals guided the process of development.

Results: As a result of the needs assessment, two goals for the intervention were formulated: (i) helping healthy pregnant women to stay within the IOM guidelines for GWG; and (ii) getting midwives to adequately support the efforts of healthy pregnant women to gain weight within the IOM guidelines. To reach these goals, change objectives and determinants influencing the change objectives were formulated. Theories used were the Transtheoretical Model, Social Cognitive Theory and the Elaboration Likelihood Model. Practical strategies to use the theories were the foundation for the development of ‘Come On!’, a comprehensive programme that included a tailored Internet programme for pregnant women, training for midwives, an information card for midwives, and a scheduled discussion between the midwife and the pregnant woman during pregnancy. The programme was pre-tested and evaluated in an effect study.