Parenthood is a normal event in which the birth of a baby temporarily upsets the internal structure of the family system as boundaries, roles, and tasks are reorganized to accommodate the new member. In understanding how interactions between and within spousal and parental relationships affect parental adjustment, concepts of development need to be considered. Described in this paper is one way of conceptualizing and measuring family interactions in the childbearing family. Specifically discussed is a self-report method intended to assess men and women with regard to (1) changes in the marital relationship from just before to 5 months after the birth of the first child; (2) the association between individual functioning and the marital relationship before and after the birth; and (3) the interactions among parents' coping, perceptions of infant temperament, and the marital relationship after the infant's birth. A proposed developmental study implementing the model is described. (RH)