Heroin baby - from a devastated Grandmother

Hello. I am writing to you to first of all tell you that I have found some comfort reading your blog. I know I am not going through this alone which makes it a little more bearable. 
My son died of an heroin overdose 6 months ago and his girlfriend is due to give birth to my grandchild soon. She is a heroin addict also and the child will be born a heroin addict. It disgusts me that drug addicts self neglect but to thrust this dirty vile drug in to an unborn child is sick. I have no words. 
The baby will go straight in to the hands of the authorities when he is born and I am in touch with social services. I am in my 60's and not in great health otherwise I would have fought hard for this child but I have to be sensible. Even so it breaks my heart.
I adored my son because he is my son but I didn't like what he had become. His addiction made me very very ill and I suffered a stroke when he died. 
I used to shout at him telling him to stop but I now know that it wasn't as easy as that. 
Even though my son is no longer here, I still have plenty more heartache to come and I am powerless to help my little grandson who will be born withdrawing from heroin. If I may ask please don't publish my real name. With all my love and thanks.