How long do babys go thru withdrawal?

I am adopting a relative's child. She is due on August 20th. She was using meth until a month ago. I have done a lot of research and am prepared for the worst, hoping & praying for the best. My question is...will the baby still be going thru withdrawal at birth? I feel kinda silly asking, but I'm curious. It sounds like the withdrawal process takes a long time for babies born addicted, but at least this baby will have the last three months without meth. Emom is in a safe facility, so I know that she's clean. Also-can someone tell me a sling brand to use? What about swings? Any other advice?