Your daughter has been on a maintenance med under the care of a physician. She was not in active addiction shooting H and/or popping pills running around in shady places trying to get her fix.....not eating properly...neglecting her health. So chances are the baby will be born healthy. Many many women give birth to healthy babies on subutex.
As long as she follows the doctors orders about doses....does not try to come off it without the doctors knowledge or being closely monitored she will give her baby the best chance of being born healthy.
More prayers going up.