Why did he look and say that? I will answer answer yours if you answer mine.?

Okay so in my second period class I sit between my two friends, B and A. Me and A were talking about baby showers and B gives us this look like what are are you guys talking about and I told him as a joke that I am pregnant with twins and he looks at my stomach, smiles and says " Aww". Why did he look and say that?