# you barren woman ... children of the married woman

Yahweh telling the people of Jerusalem to rejoice because there will be many people living in Jerusalem again is spoken of as if Yahweh were telling a barren women she is going to have many children. 

# For the children of the desolate one are more

"For the children of the desolate woman will be more" 

# the desolate one

Here "desolate" means that the woman's husband had rejected and abandoned her