What happened to Kushina Uzumaki?

Kushina Uzumaki was the second kyubi host. At the time of her pregnancy, her seal is weakening because a female host with pregnancy will be at her weakest state and anybody could force-steal the kyubi from her. After she gave birth to Naruto, Madara Uchiha came and force-stole the kyubi from her. Minato (Naruto's father) fought him off and sealed the fox into his newborn son along with a little of his chakras and the rest of Kushina's chakras which the sealing technique took both of their lives.