I Was 4-5 Weeks Pregnant When I Smoked Pot. I

I was 4-5 weeks pregnant when i smoked pot. I didnt know i was pregnant until a week later.. My urine sample came back positive for marijuana and they told me when i give birth their going to test the baby and if it positive their going to call CPS. I am now 12 weeks and scared that its going to be in the babys system at birth. How long does it take to clear out of mine and babies system?