In countries such as Canada or the US it is effectively illegal to ask any personal questions in a job interview (religion, age, social & family status, ideology). In Spain those kinds of things are the first questions a woman gets asked, and for most common jobs, children (present or future) in practice mean she won't get the job. I am not aware of any restrictions that discourage this practice or allow her to safely refuse to answer.

I know of at least one employer who privately boasts that when he needs to hire a woman, he will only hire a lesbian, to avoid this issue altogether.