I've hurt my children in a horrible way but I can honestly say that the only "drugs" I had when I was pregnant with them was nicotine in the first month with DD1 and caffeine with both (in limited amounts-for headaches as soda and coffee made me ill). I did have an epidural with DD1 and some cocktail of medications with DD2 (no epidurals in that hospital unless you were having a C-Sec).
One of the biggest things I can say is that when I found myself struggling with mental health issues I took steps to keep from having more children. I love children, I love my children but for some reason my brain short circuited and I didn't want to put any other children through that. Things definitely got worse before they started to get better.
I have also started to realize that taking care of my mental health is thing one, and that no matter what else I think I want, I need to make sure my head is on straight.