Als Quelle benutze ich die englische Narutopedia, die eigentlich relativ treffsicher!
Ich bin der Meinung, dass Karin nicht Saradas Mutter ist, weil :
Es folgt einen kleinen Wall of Text in englishe Sprache
Aus Saradas Sicht
Sarada was born to Sasuke and Sakura Uchiha. Since Sakura refused to leave Sasuke's side during his journey, even while she was pregnant, Sarada was born in one of Orochimaru's hideouts with Karin's help as a midwife. As such, no records of her birth were available at the Konoha Hospital.
Sakura explained that she was aware of Sarada's doubts and insisted that she was her mother. Sarada agreed, adding that the only thing that mattered was that their hearts were connected. Turning her attention to her father, she asked him if he truly believed that he was connected to her mother, which he confirmed by saying that both he and Sakura have Sarada as a daughter, moving the young Uchiha to tears.
Aus Karins Sicht
Upon learning that Suigetsu used a umbilical cord he thought belonged to Karin for a DNA test to help Sarada uncover the identity of her birth mother, Karin was furious. She informed him there was no possibility she was Sarada's birth mother because she helped Sakura deliver her daughter. She further elaborates that the umbilical cord was from Sarada and Sakura, and that Sakura had travelled with Sasuke during her pregnancy and helped with the delivery when Sakura went into labour. When Suigetsu asked if that meant she was over Sasuke, she was silent for a moment and said all that mattered to her was that Sasuke was happy and that she had become friends with Sakura. Karin then tells him he owes Sarada an apology and should start by giving her a new pair of glasses, since she seems to have outgrown her current ones.
Quelle
http://naruto.wikia.com/wiki/K…ge_and_the_Scarlet_Spring
Englische Wikias haben die Angewohnheit sehr sehr genau zu sein, nahezu alles ist mit Referenzen belegt. Wobei die Genauigkeit sich nach dem Bekanntsheitsgrad des franchise und der Größe der Fanbase richtet