You are not going to like the list of things that can harm a baby prenatally.. lol. Raw eggs, raw fish, lunchmeat (unless heated), fish that have high levels of mercury, soft cheeses all come to mind. Also, stay away from cat litter. And of course drugs and alcohol.
When I teach about this in class, I usually talk about how... yes people sometimes do these things and everything turns out fine, but if it were me, I'd be careful because if something could go wrong, I know I'd blame myself on doing whatever I did that was potentially harmful.
Good luck on your quest, that is so so exciting!