Relationship ?

Yes, I would be concerned, but I would bite my tongue. She's an adult and free to make her own mistakes.
As long as she's not relying on your for financial or other support, that is. If she IS, you have the right to express some concern, or better still, tell her nicely but firmly that you won't be able to help her any more.

Of course I would. Does pregnant for the second time mean she's already had one of his babies? Or she's had another man's baby? Or no baby? When I was 21, I'd not have listened to a word my parents would have said about anything but they weren't talking to me anyway. Probably because they knew that. 

She's 21. She can do everything you can do but run for President now. Lol Leave her alone. 

Yes.............