With ds #1 I completely didn't know. I had been getting sporadic "gas" pains all day, including as we went out for a Mexican dinner It was only at 10pm that night when the *regularity* of them made my brain perk up and take notice (and by then they had started coming every 3-5 minutes.) I didn't have any BH prior to this, and spent some time wondering if that was what was happening - but nope it was labour alright! (I still laugh at myself that after all of the reading and prep I thought I'd done I was on google at 10.30pm asking "what does labour feel like"?) And to think I'd thought I was in tune with my body !