I have had that my whole 9 months so it wouldn't be a sign for me BUT my sister got nauseous and headachy the night she started to go into labour... I think anything and everything is possible with labour sometimes
I puked the night before my daughter was born...my MIL and I were watching(of all movies) Look Who's Talking, and we were eating popcorn, and I wasn't feeling well so I took a bath. Puked IN the bathtub...had contractions all night long that were completely painless, just a tightening of my belly...was supposed to see my doc the next afternoon, but they squeezed me in that morning. I was 35w5d, and already 3 cm dilated. He said "I'll meet you over at the hospital, young lady, you're having a baby."
I've read that as well. I lost my plug yesterday and tonight I went pee then about 15 minutes later I sat on my bed and felt like a peed a little. Had to go change myself. Been freaking out since because of other things like: nausea, diarrhea, headache, lower back pains, ect. Don't know if I should call l&d myself. Let us know how it goes for you!