Baby-farm, baby-farmer

Does anybody know the origin of the words "baby-farm", "baby-farmer"? What have infant babies got to do with farms?

It could be based on the Nazi German system whereby 'true, blue eyed Arian' men, often SS members, were paired off with a similar female in special camps/facilities in order to breed a 'purer' Arian super-race. These camps were described as 'baby-farms' by some sources.

Some women with good child-bearing, have baby after baby as surrogates for women who can't go to term. I think I've heard that described as "baby-farming".