How far can cps take this?

I just delivered my son about 3 weeks early and my urine tested positive for marijuana. I smoked a little almost a month ago so I wasn't smoking everyday. The nurses tested my son and he came back negative for marijuana. But I was interviewed by a hospital employee and she said she had to give this information to CPS. Now I live in California and my husband has a marijuana card and I plan on getting mine after 6mos to a year breastfeeding which would make it legal for me to smoke pot. I plan on breastfeeding so I was wondering how far can cps take this case? And no I don't plan on smoking anymore until I'm done breastfeeding.