I went for a job interview when I was 12wks as an IVF surrogate- didn't say anything at the interview- they hired me and I waited even two weeks in to first show them why I was the best worker for the job.
They all thought it was amazing when I broke the news and our whole office talks about it openly now- asks me questions and become intrigued! I'm due in August and will be taking a little time off for birth and recovery which I guess is a little different but the same principle applies.
Discrimination does exist- legal or not, but it's much harder to discriminate once a company has already invested in you: and so it should be- you should be hired based on the fact you're the best for the job not because you are ttc or not good luck! Tell them closer to needing time off.