I know someone who didn't find out till 14 weeks - she thought she had a hernia and when she had a scan to confirm they found a baby instead. She was a woman who had been married for well over 10 years already by that point and her and her DH didn't want kids so it was a huge surprise for them. My own mum didn't have her last pregnancy confirmed until she was 20wks. She was 38 and she thought she was starting to go through menopause. As for me, I had a suspicion with my first because I just felt so wretched and it was the only thing it could be. We weren't trying either as we'd only just gotten married and we wanted to wait a while. But it would have been about 5 weeks and I had it confirmed at 6 weeks.