Hi, smoking, alcohol & drug addiction affect almost all the systems of the body. They do cause damage to the sperm count & sperm quality. Since half of your babies genetic compositon is contributed by your sperm, this can have an adverse effect on your baby in case a damaged sperm happens to fertilise the egg. So your GF will need an intensive screening tests to know whether the fetus has any such defect, in case she wants to continue the prenancy.