The study investigates the effect of the 'Mother and Baby' (M&B) program on the psychological health and well-being of new mothers 6-10 weeks following the birth of their baby. The M&B program is an 8-week program of group exercise and education sessions provided by various health professionals. The design of the study is a comprehensive cohort design, including a randomised controlled trial. The primary outcome measure is the Affect Balance Scale. The hypotheses are: