Ask to see the anaesthetist at the pre-surgical appointment and explain the problem and ask what they can do about it. I was very worried about this as another friend had problems during her CS but I chatted about with the anaesthetist and he said there are some very specific things they can do to help it if your blood pressure drops. I didn't have any probs with it at all, but given your past history this is something to need to bring up - at the pre-surg appt AND on the day. Good luck!