Old Testament verses other than Genesis 3:15 speak of the "seed" of a woman. How, then, does it indicate a virgin birth? I am researching prophecies about the virgin birth of Jesus in the Old Testament and am currently trying to find answers on specific issues.

Genesis 16:10; 24:60; 4:25; Leviticus 22:13; 1 Samuel 2:20-21.   

The above verses talk about women and their "seed". How do these verses and prophecies agree with the prophecy of Genesis 3:15 if this verse refers to the virgin birth?

And how does the "seed of the woman" in Genesis 3:15 differ from the 'seed of' the women mentioned in all the other Old Testament verses? 

Can anyone enlighten me as to how these verses fit together?
Women and their seed is merely a reference to the women's offspring, children, and/or posterity. 1 

Gen 16:10 is in reference to Sarah's descendants being unnumerable

Gen 24:60 Rebekah's descendants will possess the gate of those that hate them

Gen 4:25 talks about Seth being another son since Cain slew Abel

Lev 22:13 mentions a priest's widowed daughter without a child

1 Sam 2:20 Elkanah and his wife will be blessed with children as they have prayed them

Gen 3:15 is about enmity between Eve's descendants and Satan's descendants/followers

None of these prophecies explicitly refer to the virgin birth. If it is your understanding that it does, none of the other references agree or disagree, as they are about different people.

1 http://biblehub.com/hebrew/2233.htm