Is there any reference to the gender of the *nephilim* in the Bible?

From what I understand they have been created by sons of God with the women of men ([Genesis 6:4](http://biblewebapp.com/study/?w1=bible&t1=local%3AENGESV&v1=GN6_4&w2=bible&t2=local%3Aheb_wlc&v2=GN6_4&w3=bible&t3=local%3Agrc_lxx&v3=GN6_4) ESV):

> 
> The Nephilima were on the earth in those days, and also afterward, when the sons of God came in to the daughters of man and they bore children to them. These were the mighty men who were of old, the men of renown.  
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> a Or *giants*
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> 

But were they only men or were there also women giants? If they were only men how could this be explained? Were the Sons of God capable of choosing the sex of their offspring?