Lesbian here, but not a mom. Congrats!
In this day and age, it's unbelievable that anyone makes any comment of any kind about a kid's origins. On my block alone, there are:
* 50+ parents of a 2 y/o from Colombia
* White parents of a Vietnamese girl
* Mixed-race parents (neither Asian) of a Chinese girl
* Gay male parents of a Chinese girl
And one straight couple who SERIOUSLY look like siblings
I think the best answer to any moronic MYOB question is either a) the truth, if you feel like sharing or (b) the classic innocent eyebrows-raised "Why do you ask?"