Oda was asked what is Luffy’s mother like? Here is the answer:

John Irons: What is Luffy’s mother like? Was she beautiful? What happened to her? Did she die when Luffy was a baby?

Oda: I think she’s alive. I’m still thinking hard about this. [Laughs] But if she does appear in the story, then she’ll be a very tough-looking woman. And strict. There’s no way that she’s a beautiful mother. She’s got this typical middle-aged woman’s permed hair.