He shouldn't and that would be against the Pregnancy Discrimination Act (presuming it applies to your company). On the other hand, was he asking because he is concerned for you or is he just a jerk? If the former, you should tell him it was offensive and ask him not to do that again. If the latter, tell him it was offensive and you have reported him to HR.
Answered on Jan 14th, 2014 at 12:23 PM