If a woman continues to use drugs while knowingly pregnant and refuses to seek treatment then yes, I don't see why she wouldn't at the very least, have her maternal rights severed until she stabilizes.
Under the supervision of a Dr. That is one thing. Knowingly self medicating despite the obvious risks is anotther

[[ In the Wisconsin case, she wasn't just "allowed to take potentially harmful drugs under the supervision of a Dr." She was FORCED to take potentially harmful drugs despite having gotten herself clean. Because that fetus had a "representative" who got to decide instead of the mother herself. HOW does that not outrage you? ]]

Again- no qualms with how either of those cases were handled (except in Rowland's I wish the Drs had authority to implement C-section against her wishes and save the other child.)

[[ a woman wishes to avoid unnecessary surgery if she can. She seeks to deliver vaginally but is denied access to any hospital unless she agrees to give up her right to medical decision-making and schedules cesarean surgery. Her attempt to labor and delivery at home is discovered and she is taken into custody by a sheriff while in active labor, transported against her will to the hospital with her legs strapped together, and forced to have the surgery;Despite knowing that forced cesarean surgery could kill her, a court orders a pregnant woman to undergo that surgery – and both she and the baby die;A hospital obtains a court order forcing a woman to undergo cesarean surgery. Her opposition is so strong that hospital staff ties her down with leather wrist and ankle cuffs while she screams for help.
http://en.wikipedia.org/wiki/Pemberton_v._Tallahassee_Memorial_Regional_Center ]]

I have no qualms with the decision reached in the Pemberton case. Attempting a VBAC at home is incredibly high risk, and I don't believe the birth plan of the mother > the health of the fetus.