broccoli stalk?

I'm 31 weeks and Glow tells me the baby is the size of a broccoli stalk.  What does that even mean?  Hahaha.... I thought the "stalk" was the stem.  It better be a big stalk, then, since it's supposed to be bigger than a cabbage (30 weeks).
Whoever chose all these fruits and vegetables is just confusing me, to be honest.