The existence of maternal wellbeing is characterised largely by the absence of depressive symptoms and mental illness. This study aimed to develop a positive measure of maternal wellbeing to be used with new mothers to determine mental health levels. Participants (n=323) completed a pilot measure that consisted of sampled and purpose written items endorsed during phase 1 (total n=51). The scale was then analysed for reliability and consistency. During phase 2, a new measure of maternal mental wellbeing was piloted. The C-MEWS score was compared with total sores for the Edinburgh Postnatal Depression Scale, the Warwick-Edinburgh Mental Wellbeing Scale and the General Anxiety Disorder questionnaire, and successfully discriminated between them. The measure demonstrates high reliability and good validity, taking into account various external factors. This study leads existing research closer to a conceptual definition of maternal wellbeing and a possible new approach to maternal mental health.