Well, you know, it’s because her water’s broken. Out of the clear blue, with not even a mild cramp, in the most embarassing public place possible.
And once they get to the hospital, they never show them connected to the fetamonitor or having any of the other annoying crap they do at hospitals done to them.
I was amused by the episode of (I think) Roseanne, that actually had the character get an epidural and not spend the whole time groaning in agony.