Sorry haven't read all of the replies, but I definitely see some judgement. In my own personal experience, I was surprised at how much professionals/healthcare providers can be judgemental, or at least treat you palpably differently to someone older. And I wasn't even a teen mum! (Gave birth to DD when I was 21).
My midwife was horrendous to me in labour, it really put a downer on my birth experience :( She literally rolled her eyes at me on occasions, like when I was delivering the placenta, implying very clearly that she thought I couldn't possibly know what was going on. This happened with a lot of other things too. The first health visitor I saw was also so tactlessly rude that I was literally speechless with anger, and it wasn't just the post birth hormones!
Saying that, I did notice a strange correlation between my confidence as a mother and the way people treated me. The next health visitor for example, was really nice, I think she could see how comfortable I was with baby. That does make me sad though, because surely young mothers who look like they need support are the ones who need to be isolated the least!
And as for my own personal feelings towards teen mums, I definitely don't judge them for the one factor of being young, however I can't help but judge any mothers who aren't very nice or patient with their children, it really upsets me. I've unfortunately seen that from parents of all different ages though, and I think the common factor is a lack of support, either from family, partners or the system. Just my two cents though!