I do not see why, while he feels no attachment for Karin, they would have had a child together. From that, me comes to Sakura there: would she have easily really agreed to educate the girl of Karin? Why Karin would not she even have been able to educate her own daughter? How is possible for Sasuke to marry Sakura but leave Karin pregnant with his child ? How can Sakura raise her beloved one’s kid instead of creating her own family?! She is one of the best ninjas in the world and she abandoned her own life and career just to raise the kid that the love of her life has with an other woman?! That has for me no sense.