"Okay, well, don't freak out, but, uh... I'm... ow. I'm on my way to the hospital right now, because either I just peed my pants or my water just broke."
"And last time I checked... ow... I don't generally pee my pants. So, I'm pretty sure the baby is on their way. I'm like, 99% sure. So... ow, *squee!*! I'm driving myself right now to the hospital. Could you maybe meet me there?"
"Right. Oh, and before I forget, for the love of God, don't drive like a madman. It won't do the baby any good if you die before meeting it."