I had the same concerns re my birth as Ive had similar reactions to pethidine. On my birth plan - I actually wrote that I was allergic to pethidine and morphine and made them write it down in my medical file too. Fentanyl as mentioned was the other alternative which they ended up using. Ive not had a C section for birth, but had a similar surgery for a health condition - this was when I had the pethidine given to me and reacted badly. I just ended up going without pain meds after that surgery and survived ok.