I hope this helps some until someone who has had chronic pain during pregnancy comes along.
My medical book shows that your Duragesic is "uncertain safety in pregnancy, no human studies were performed" and that it is "believed to be safe during lactation." For your Percocet it shows the same during pregnancy, but for lactation it is "generally regarded as unsafe." It also says "for patients with chronic pain all opioids are considered unsafe for prolonged periods or in higher doses at term."
I was given this book by a doctor I worked for, so I know it is one that they use or have used as a reference.
Wayyyy back when I was pregnant I was only allowed to use Sudafed and occasional Tylenol....luckily I didn't have chronic pain until years later. During my daughter's pregnancy a few years ago her OB had given her Vicodin or Lortab for occasional use, she was just starting with her back pain (she's following in mama's footsteps with a bad spine).
cervical fusion 2006, with great result
lumbar fusion 2005, with continued pain