Hi and welcome back !!
I know we have had this topic come up b4.....and I know some Drs will prefer you to go with the C-section....but do make sure your OBGYN knows all about Chiari and the surgery you have had...as I have heard a few that after childbirth are getting symptoms back.....to minimize the possibility, is why Drs suggest a C-section.
Just the changes your body will go thru can trigger some symptoms to return, if just during a portion of the pregnancy....
I had my daughter b4 my DX so I can not give my personal experiences on this.... I am sure others will share theirs.