What mother says this to a pregnant woman?

During our staff meeting, this interaction took place:
Coworker: (while whispering w/another coworker & pointing at me) Gena, how much weight have you gained?
**OK, I should have stopped this conversation right there but I was so caught off guard I fell for the trap**
Me: (Insert huge amount of weight gained here)
CW: Wow, why have you gained so much?? I only gained 25lbs with my son
Me: Uhh, I don't know? My mom gained almost 70lbs w/my oldest brother, so at least I've gained less than that.
And then I proceeded to walk away red-faced and make an attempt not to cry in front of all my coworkers. Seriously, who asks another woman how much weight she's gained? Especially someone that's had a baby. From now on, I'm locking myself in my office so no one is tempted to repeat this conversation.