If you stopped smoking marijuana at 3 months pregnant will it appear in your placenta or new born when you give birth?

Pot/pregnant. Not likely, but I recommend close monitoring by your ob/gyn. Since u smoked during first 3 months.
Probably not. We look for it in the first poo, which starts forming just after about 12 wks. If you truly stop, it will not be there. They wouldn't look for it unless you showed up on a list with child and family services or if you are known to have a problem.