Did Jerome’s doctrine of Mariology affect his translation? In a recent Q&amp;A on Hermeneutics.SE, I made an arguement that carried the implication that Jerome's translation of κεχαριτωμένη ('favored one’)† as gratia plena ('full of grace’)† in Luke 1:28 was misleading, conflated as it is with another phrase that has a different meaning in Greek. It was rightly pointed out that I didn't discuss the reason why Jerome made that decision.  Since I don't see an obvious linguistic explanation,* I wondered if there might be a doctrinal and/or sociological explanation. 

In another Q&amp;A on Christianity.SE, Jerome is cited as a key proponent of the doctrine of the perpetual virginity of Mary. I'm not sure whether that has anything to do with the appellation “full of grace” or not. Other aspects of Mariology seem more relevant.

I'm interested in knowing:


What did Jerome believe about the immaculate conception?
What did he believe about Mary as Mediatrix of graces?
Did he use Luke 1:28 in defense of any Mary-related doctrine?





† Glosses extracted from ESV and Douay Rheims, respectively.


*Particularly with regard to translation decisions, even if I disgree with the choice, I can sometimes see the reasons for a different decision. Here I don’t.
This isn't a full-blown answer to your question, but instead a partial one.  I suppose one would have to write some sort of magnum opus to answer all three of your questions in a way that does justice to them.
But as a sort of beginning, I do know that translators over time have moved away from away from the Vulgate because of its emphasis of Mary in places she does not belong. The best known example of this is Genesis 3:15. To so many Christians this is the protevangelium (the first gospel promise pointing to Christ) in the bible.  Genesis 3:15 reads as follows:

‏”וְאֵיבָה אָשִׁית בֵּינְךָ וּבֵין הָאִשָּׁה וּבֵין זַרְעֲךָ וּבֵין זַרְעָהּ הוּא יְשׁוּפְךָ רֹאשׁ וְאַתָּה תְּשׁוּפֶנּוּ עָקֵב׃“‎ (Gen 3:15 BHS-T)
“I will put hostility between you and the woman, and between your seed and her seed. He will strike your head, and you will strike his heel.” (Gen 3:15 HCSB)

You'll notice the &quot;he&quot; vs. &quot;he&quot; construction.  But in the Vulgate we find this:

“inimicitias ponam inter te et mulierem et semen tuum et semen illius ipsa conteret caput tuum et tu insidiaberis calcaneo eius” (Gen 3:15 VULG-T)

Instead of &quot;he will crush your head,&quot; it reads &quot;She (ipsa) herself will crush your head.&quot;  In this we see a strange, unfounded translation of a clearly masculine word in the Hebrew (הוּא) into a feminine word (i.e. Mary).
I hope this helps, at least a little in working toward the bigger, better explanation this question deserves.