I'm very glad to be only 20 mins from a tertiary level hospital - I couldn't imagine being in the position to be airlifted somewhere else!
I am(was) mostly a desk jockey for work, but I think stress was a much bigger factor than I realised at the time. I was already under close supervision, with a cervical suture and fortnightly scans before being diagnosed, so stopping work was really a no brainer.
Triggers: stress, dehydration, full bladder, standing, most physical activity.
Incidentally, I saw the hospital obstetric physio on Monday, and she also advised that pressure on the uterus/belly is a known trigger, so abdominal support wraps/socks are not recommended. She also said to be very wary of engaging your core muscles to go from sitting > standing and also when getting in and out of bed. On top of that, no pelvic floor exercises! I wasn't doing them anyway, because of the suture, but just in case any of you are!