How long do babys go thru withdrawal?

My daughter was born exposed and tested positive for multiple substances meth being one of them. It took her about 6 weeks for her to detox but she was positive at birth. I am not 100% sure but I think the baby would detox with the mom if she stopped using while she was pregnant. Don't quote me but if it takes 4-6 weeks out of the womb I don't think it would take much longer inside the womb. But that doesn't mean there won't be any other lasting effects, not that I am saying that there will be....you just can't be sure KWIM? My daughter's main symptoms were also grunting like she was in pain, her body would tense up and tremor, she would sweat a lot and didn't have good skin color (grayish skin tone), she didn't sleep well and wasn't easily consoled. Those symptoms were almost non existent after 4 weeks and totally gone by 6 weeks. Now that I am thinking back I honestly barely remember that time....she is a beautiful, gregarious, hilarious 15 month old with no developmental delays that we can see so far.ETA: my daughter's bmom is my cousin! We don't have a ton of contact with her either. It varies from month to month.