I doubt you are bugged, her babies vanish into the nursery then into the general population (you should notice more goblins hanging around) I think it works out as something like one goblin sprite per 10 population.
Check your ledger and see if your tribute is going up.
Edit: actually check your "Book of Girls" it tells you the goblin population in Shakalas section... Goblins tend to die easily so don't expect it to be a straight addition (babies + previous births), there will be a death subtraction going on.