"The best part of being a mom is his slow smile he gives me every morning when I say, 'Good morning,'" Blair, 39, said at last night's amfAR Inspiration Gala at Chateau Marmont in West Hollywood.
"I'd say about 45 minutes a night is what I sleep," she told us. "It's a special situation and I cry. Mama cries."
"This child is a saint," Blair said of 3-month-old Arthur. "[But] it's horrifying. You're too tired to enjoy how precious this time is...It is very challenging."
Blair says she probably won't dress up little Arthur for Halloween.
"What do you do with a dressed-up baby?" she laughed. "Give him a bath and put him to bed? It's all kind of silly."
Not that she didn't think about a costume.
She smiled, "I was trying to have him go as a turtle, but they didn't have infant turtle costumes."