Oh yeah, I feel strongly about this issue.
An IV drug user wouldn't want to divulge this information (their drug use) to ante-natal services as they would probably have to inform docs.
The best thing someone can do is seek help.
First trimester is the danger time for miscarriage due to the 'ups and downs' of opiate use in the system - going through withdrawals when hanging out will harm the foetus.
The baby could be born opiate addicted if the mother is having a raging habit and then baby will need special care nursery. But this is monitored.
Many women are fearful of seeking help whilst pregnant as not wanting to have a baby whilst on a methadone program. they fear the stigma attached. and feel maybe they can cut back their use of heroin or other opiates and therefore the baby will be born ok.
It's all such a hard road.

And what really shits me is these men don't have to cop any of the blame or stigma attached. did you see this woman who is pregnant and prostituting said the man hasn't stuck around.(ok I realise she obviously had some sort of habit prior to being pregnant) It is so typical. Now society looks down their noses at this woman. Let's find the male and string him up and pull his testicles out of his mouth!!
Nasty nurse here's to you!!