Runners - when did you stop running?

Around what week did you stop running? What was your reason for stopping?

I'm an ultramarathon/marathon runner, 24 weeks with my first pregnancy and things are starting to get a tiny bit uncomfortable. I feel a lot of pressure while I run, then I notice I'm incredibly sore in my lower abdominals/pelvis area for the rest of the day. If I do a longer run, the soreness will be there for a few days. I'm stubborn and want to maintain my running fitness, but wondering when it makes sense to transition to strictly walking and hiking.