It might be, but vomiting and diarrhea in late pregnancy is common regardless. Many women never even get sick before labour or do in transition.
It is possibility that it is a sign of labor
That's the thing. I threw up maybe once or twice in my first trimester and I think that was from adjusting to my prenatals. So I guess i'm just hoping it's a sign.
Those first trimester symptoms seem to come back. With my first I did vomit only 1 time a few days before I went into labor. With my second pregnancy I just was a little nauseated but never vomited. I think that happened around 36 or 37 weeks.