Devaki was the princess and daughter of Devaka, younger brother of King Ugrasena of Mathura. Kamsa, the cousin of Devaki imprisoned her with her husband Vasudeva because there was a foretell that one of their sons would kill Kamsa. Kamsa then killed six of the Devaki`s son in the prison.
The seventh son Balarama was saved by being transferred as a foetus to the womb of another woman. An incarnation of Goddess Yoga-Nidra or Maya was placed in Devaki`s womb instead.
The eighth son was Krishna, who was Vishnu`s incarnation. He was born at midnight and his father Vasudeva carried him to neighbouring village Gokul in the shelter of Nanda and Yashoda. It is believed that Krishna was not born by any sexual connection between Devaki and Vashudev, but was transferred to Devaki`s womb.