My Step Daughter Is Pregnant And Is Now 34 Weeks

My step daughter is pregnant and is now 34 weeks she has used meth for most of her pregnancy. She seems to think that if she stops using a few days before she delivers the baby will not test positive at birth. Will the baby still test positive for meth at birth even if she stops using now? How long after birth will it take for her baby to expel the meth in its system? And what is the best test to determine meth and amount of exposure during pregnancy?