I mean really, why?
It strikes me as already putting your child into a box before it's even born. And talk about a bad start for a kid - I really wanted you to have different genitalia because I've got some weird idea that that's what determines your character, behaviour and relationship with me and of course my parenting can't be expected to have as much influence as your genitalia.
FFS.
Sorry I know there may sometimes be legitimate-ish reasons for this (you've had 5 boys already and you want a girl, you're thinking of the future when you're a MIL etc.) but the woman I know hasn't got such reasons - she's just a fuckwit and I need to vent because I'm sick of her saying (in front of my DS as well), that she only wants girls. Bear with me. 