Thank you for this discussion ladies.
It is always useful to revisit the latest research on this topic, if there is any, and the cultural/regional differences in policy around care of mother's who use MJ.
I am curious, how are these positive drug screens obtained?
With maternal consent?
Are they universally done on all mothers?
If so, when?
In the part of the world where I live, MJ use is tolerated, though not yet "legalized" as far as I know.  That means that just reports of use by mother would seldom result in action by child protective services.  There would have to be other concerns than just MJ use by mother - yes even a breastfeeding mother.
I live in small resource based town, that is economically suffering and where there is likely a good percentage of the population involved in MJ growing or transportation.
In public health we take a harm reduction approach and the conversations are very interesting when you work alongside folks who use.
In my experience mothers are always looking ways to make changes that are healthier for their infants, and for those who can't abstain or who have done what they can but are still using they talk how their MJ use keeps them from returning to their crack addiction, for example.  Or manage the effects of trauma.
My messaging is a combination of key messages from alcohol and smoking.
There isn't alot of research on breastfeeding and MJ use as Nikki points out, what is out there is often confounded by poly drug use and very little that is out there shows harm.  There is some research on neurological changes, increased risk of schizophrenia and executive motor delays for example, when mother uses in pregnancy.  That's my understanding, please share if you know more.  
Lack of evidence of harm is not a recommendation to use, however!  I just believe we have a prerogative to tell parents honestly what we know and what we don't.
I also tell parents that THC likes fat and breastmilk is full of fat, so it transfers easily to baby.  The younger the baby, the greater the "dose" to baby and the more difficult for baby to process due to liver immaturity.  
If you are high, the THC is psycho active and would have the same effect on baby.  Being high and caring for a baby is not a safe combination, so who is available to care for the infant who is sober?
We give all the same messaging we give around smoking and minimizing infant exposure . . . we don't have evidence but likely MJ use increases risk of SIDS, asthma, etc . . . 
We talk about safe(r) sleep as Nikki describes as many in our population co-sleep and/or room share.
We talk about what it means to raise a child in a household where Mj use is normalized . . . many come from situations in which they grew up seeing family use.  This is often apart of a conversation about substance abuse and family history, not just limited to MJ.
I also let famlies know that their baby, along with them, will test positive for THC metabolites for a long time, weeks.  And if they already have child protective services already in their world they may want to consider the implications.
So those are some things we discuss, off the top of my head.
How does that fit with what others are saying who take a harm reduction approach?
Warmly,
Tina
Port Alberni, BC
Canada

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