Final answer:
The period between the wedding and the birth of the first child is known as the establishment stage in the family life cycle.
Step-by-step explanation:
The stage of family development that extends from the wedding until the birth of the first child is referred to as the establishment stage. This is a part of the family life cycle, which accounts for a series of predictable steps and patterns families typically experience over time. Initially developed by Paul Glick in 1955 and later elaborated by his colleague Evelyn Duvall, these stages outline the progression of family life from marriage to the growing of children and beyond. The establishment stage specifically encompasses the period after a couple has married but before they become parents, focusing on the consolidation of the marital system and adaptation to life together.