Tony had slid in toward her in quite a bit of commotion and it distracts her from her pain enough because she's laughing so hard. When she gets control of herself again, she answers Tony's question.

"I do believe my son is coming into the world today," Sansa says, rubbing at her lower back. "Things have actually started to hurt today and while I've had aches and pains, this is different. I've been walking to see if the pain relieves and it hasn't broken yet. Still, my lady mother told me it was good to walk when I was close to my time."