Now that I'm over 35 (but childless), I've taken it as my duty to privately and gently advise younger colleagues who ask that question that there is absolutely no good answer, especially if the person being asked is a woman over 30.

My flippant answer: "Well, you can't exactly order them from Amazon..."

In my case: yes, I wanted children. The wanting does not always lead to the getting. Any further details from me on this subject might ensure that you never, ever ask that question again, unless you're in a serious romantic relationship with that person.

I bring up children in almost every interview at some point. I want to subtly hint as to where my allegiances lie. It's better when my son has to come home sick from school, and my wife is in some other part of the country.

In the UK that question can't be asked or it opens the employer to liabilities.

While it may not specifically be illegal in the US, it's certainly opening the interviewing company up to huge potential liability. All the interviewee would have to do would be to show that it's more likely than not that they were intending to discriminate based on gender / likelihood to get pregnant.

Definitely not a question that should be asked.