Babies born to drug addicted mothers?

I am writing a paper on drug addicted babies (meth, cocaine, heroin). Everything that I have read leads me to believe that every child born to a mother who abused drugs during her pregnancy is going to have either long term or short term issues. Is this true? If not, what factors determine if the child is going to have major issues or is it a “luck of the draw” (for lack of better words) kind of thing?