These people are dumb.
People think it's Sasuke DNA but it's am umbilical cord for Christ sake. Whether it is Karin's or Sarada's, it doesn't matter. I did my own research, and apparently Japanese parents keep these umbilical cords for certain reasons, so without a doubt Karin is the mother.
The whole Gaiden and this chapter says so, in the term of how DNA/Genes aren't the only thing passed down by parent to child, that and Sakura's conversation with the leader speaks volumes on her not being Sarada's biological mother.
The birth records, keeping a picture of Team Taka, and the chapter before where Sakura said she was going to sit down and talk to Sarada about something, and Sasuke said it was his problem and she doesn't need to apologize. It all adds up. If it doesn't happen, well Kishimoto's red herring sucks.
Glasses ftw :bdpf:
Go to the Sasusaku tumblr tag and click on recent, and scroll ... You'll see it XD