Why does nick think questions about Daisy's little girl would be "sedative"

In that passage of F. Scott Fitzgerald's "The Great Gatsby" Nick thinks that questions about Daisy's little girl would be "sedative" because they would tranquilize or soothe Daisy.

He sees that she is distressed, with her face buried in her hands after the dinner being interrupted by the phone ringing. We are told that Daisy's husband has a mistress in New York and that she is the one calling. In order to distract her from this, Nick thinks that asking questions about her little girl, Daisy will think of her child and forget the situation with her husband and the phone ringing.