This is the 8350th most frequent Russian word.
многодетная
Having many children.
Here the word 'многодетной' describes the type of family she was raised in, indicating that it is a family with many children.
Она выросла в многодетной семье.
She grew up in a large family.
Here 'многодетная' is describing a mother who has many children, emphasizing her role.
Каждая многодетная мать заслуживает уважения.
Every mother of many children deserves respect.
In this context, 'многодетные' is used as a plural adjective describing families consisting of many children.