The answer lies in the reference in Revelation 12:2 to pregnancy. The context, however, speaks of nations raging (Revelation 11:18). God’s first word after his enemies’ initial success involved the woman and his promise that she would prevail (through her offspring) over the serpent (Genesis 3:15). The impressive sign John may see in heaven reaches back to this promise.
1 And a great sign appeared in heaven: a woman clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars.