For now, we know that Sarada is Sakura's daughter and Sasuke is the father. Leaving Karen as the deliverer. Sasuke at the beginning showed caring to Sakura for a long time.
Also since their married now, can we say that Sasuke even liked Karen? As many times as he had bitten her... I'd say if they even had a relationship that it wouldn't have been as strong as what he had with Sakura.