I've been told that the hypnobirthing mothers tend to be able to lower their BP's through relaxation & visualisation. Maybe trying relaxing things to help lower first... so bath/shower, rest etc will help your BP maintain at a reasonable level.

Pain relief is usually the first option the midwives will go for or encourage to bring down your BP. I had an epidural last labour & my BP went down to 80/50 which was dangerously low.