a couple thoughts i had.
i think the uchiha clan did have a part in the kyuubi attack as none came to konoha's aid. itachi and sasuke's parents were conveniently away. their mother could have passed on the information that Kushina was pregnant. could be how obito found out about it. Fugaku being the head of the uchiha task force should have organized a group to send for backup.
another thought was that Hashirama will be the one to heal Tsunade. he'll probably sense her chakra and head in that direction before the battle. tsunade would probably be in disbelief seeing her grandfather. hashi being impressed on how she uses her chakra to keep herself looking young or maybe its too late and he sees his granddaughter die. upsetting hashirama and making him angry. also opening up the hokage position for naruto maybe or another candidate