Dramatic Irony

What we're seeing here is a prime example of "dramatic irony," where the character speaks erroneously due to ignorance of some knowledge that the audience is privvy to. In this case, Nina thinks she's getting the stomach flu, but we, the audience, have the secret knowledge that after being pregnant for a while, you go into labor, and it hurts. Sweet, sweet irony!

P.S. I hope you've noticed that Nina's egregious lack of common sense has made it to the banner. She earned it!