Maybe just maybe.... Karin did die giving birth to Sarada... and Saruka just raised the kid as their own... In memory of their friend.... as far as the actual father... their is another person. Suigetsu..... Not to hard to believe that polar opposites attract(karin/suig) ... Just a theory.. no proof.. just a thought.
1. Karin isn't likely to have died during childbirth unless is was
exceptional circumstances i.e she was outright murdered. Uzumaki genetics demand that she have the
survivability of a cockroach.
2. Raised the kid as "their own... in memory of their friend". That makes no sense because a) Sakura isn't friends with either of them, b) Sasuke has been gone for ten years and Sarada has never met him, c) why lie about her origin?
The above is not something Sasuke would do. Nor do I think anyone would really let that fly, passing off a kid as something she's not - not when it matters, which is does when you giving it the Uchiha name.
It's not something Sakura would do either especially if the kid isn't Sasuke's, she wouldn't have raised a child biologically unrelated to Sasuke, why? Because she's a selfish ****, that's why.
3. Whether or not the pairing of Karin/Suigetsu is likely or not - I don't care. That kid is not their's - it can't possibly be likely that Kishi would draw the child of them as having black eyes and hair, with pale skin and a dinstinct resemblence to the Uchiha.
... that shit does not fly.
What is more likely?
- She's a product of Orochimaru's experimentation; with or without Karin being accomplice.
- Karin raped Sasuke.
- Sasuke knocked up Karin who was a) very willing and b) genetically superior to Sakura.