I was wondering if it is possible to do harm to an unborn child by ejaculating into a female after the child has been conceived. Example a guy smokes pot or uses other illicit drugs could their effects be transmited through intercourse. This is once the child is conceived mind you.

In all reality yes. But not in ways your thinking. The danger of second hand drugs passing into your system and across the placenta are minimal at best. But what you do have is higher risk of infection from a drug user or STD. Both of those could prove deadly. The only time the drug use becomes an issue is when the mother is exposed to it directly and it goes into the blood stream or through breast milk after birth.

Why would you stay someone who's doing illicit drugs anyway? The influence that could have on your child could be horrendus. THAT would have an effect on the kid. Just a thought.