It is typically who is able to be part of the labour force.
remove the elderly, those for who it would be illegal to work or still engaged in formal education, the so significantly handicapped no work is manageable.
You have to be looking for a job or employed to be part of the labor force count. Stay at home moms arent in the labor force, neither are students that dont want to work.
I agree moms who would not be able to work while raising babies/toddlers, or simply prefer not to, shouldn't count as members of the labor force.
However. It is very difficult to determine what makes a mom employed vs not employed. Is that by choice/preference? or lack of opportunity. Or lack of qualification, or a combination. Coming up with statistics that distinguish the two is nearly impossible.
The official rate does not only exclude moms who happen to be jobless. It excludes anyone hasn't been actively looking any more.
What is the "U.S. labor force" defined as? Is it a age group thing?