The 12 were arrested on March 26 in Tehran as they gathered to visit the families of political prisoners on the occasion of the Iranian new year.
Ten were later released on bail but instructed to report back for questioning. The other two, Khadijeh Moghadam and Mahbubeh Karami, remain in detention in Evin prison.
The One Million Signatures Campaign seeks to rally public support against legal discrimination against women in Iran. It has come under increasing pressure from the authorities in recent months.
Mothers For Peace is a group of Iranian women who campaign for peace and stability in the region.