I've heard many stories from women about how pain meds prescribed following childbirth caused a relapse or led to opiate addiction. I couldn't find any research that looked at prevalence or risk factors.
There is a greater risk of relapse of a recovering addict of pain is not properly controlled. There is always an inherent risk of relapse when giving pain medicine to a recovering addict but the other option is cruel. The individual has to have a strong program of recovery and fellowship of others to speak with for guidance when giving pain medicine.
I would never want a person to suffer. From my understanding, someone with a history of opiate addiction may need higher doses of pain medication in childbirth to achieve the desired affect due to tolerance. I'm more of an advocate than a researcher, so I was thinking of how this information could be used to promote greater access to VBACs. I just find it interesting that with the increase in opiate addiction and opiate-dependent babies, this has still never been studied.
Pain management for people in recovery is a difficult area, and under-researched. You may find this document interesting. http://www.actiononaddiction.org.uk/Documents/The-Management-of-Pain-in-People-with-a-Past-or-Cu.aspx. In particular, I think the suggestion that it is not always helpful/appropriate to distinguish between managing pain and managing opioid dependence is quite illuminating.