It's the classical trolley problem.
I imagine the typical car accident in which three 'car seat age' children are involved, and at least one is killed. Then I imagine the typical event where a family decide against a third child. I feel quite a substantial qualitative difference! I certainly wouldn't claim one offsets the other.
Personally I don't know if there's any multiplier I'd accept. I find reduction of suffering and trauma much more important to me than offset creation of life and opportunity.