Gracie - next time you see your ob, ask what the effects are of the pethidine on the baby and how it might affect breastfeeding initiation. Meanwhile, read up a bit about this yourself and compare the answers. You might find you're not satisfied with the ob answer, or the answer will influence you to go without
As much as other women say that it's your body and you should do whatever you want, it's pretty important to also think about what is good for the baby. For me, when thinking about the effects of drugs on the baby (they all cross the placenta), it swayed me even further into the 'no intervention' camp unless medically necessary. Because birth is not just about the woman, it's about the mother AND the child. Women's liberation shouldn't erode the rights of the child, and drugs don't seem to be very liberating to me, anyway (JMO).
It really did help me at the time to remember that there are HEAPS of women who birth without drugs and that I could be one of them. I was one of many who had gone before me and my body knew what to do if I could just let it, without interference of drugs.
Sorry to push my barrow, it sounds like the knockers are getting to you! IF, after deliberation and finding out about the side effects of drugs for you AND your baby, you still decide you want drugs, then that's fine - you only need to explain yourself to you and your baby, not me or anyone else In the end, you do what you need to do and you tell yourself what you need to.
Naughty ob talking you round to drugs when you've said that your birth plan is to not be offered drugs! I'm 'grrrring' away here...