How do I make a spritefont object auto-height to its content?

Hello!

I have a chat feature in a game in which I'm creating a new SpriteFont object for each line of text, and then moving all the previous lines of chat upwards by the height of the SpriteFont object, like so:

The problem is that the user may have entered more than one line of text, in which case only their first line of text is being displayed. The SpriteFont object appears to be a fixed height at the moment, and I was wondering if there was a way to have it auto-size to however many lines of text it contains.

Any help appreciated!