Ive Recently Found Out Im 28 Weeks Pregnant An Ive

Ive recently found out im 28 weeks pregnant an ive been a chronic Marijuana user until i found out and i just wanted to know that sense im quitting now will i be clean by delivery an the fact that i smoked wont harm my baby will it???? Im 5ft tall an weigh 127lbs now and i always drink nothing but water also wanted to know if there is anything else i could do to help flush my system so im clean for myself and the baby....