The virgin birth of Jesus is a belief held by Christians and Muslims. It says that Mary, Jesus' mother, was a virgin even after she became pregnant with Jesus. By the 2nd century, most people in the Christian church believed this. The idea of the virgin birth was included in the two most common Christian creeds, the Nicene Creed and the Apostles' Creed. The Nicene Creed says that Jesus "was incarnate of the Holy Spirit and the Virgin Mary" (meaning that Jesus was God in human form, and was born to the Virgin Mary). The Apostles' Creed also says that Jesus was "born of the Virgin Mary." The belief was not challenged, except by some sects which were not very important, before the Enlightenment theology of the eighteenth century.