Gabriel answers: do not fear, grace is above nature
While the most holy Virgin was thinking these things over within herself, the Archangel settled her questioning with words like these, saying to her: The Holy Spirit will come upon you, and the power of the Most High will overshadow you. Therefore the holy one who will be born of you will also be called the Son of God (Luke 1:35). And do not fear, Mary: for I have not come to strike fear into you, but to drive the cause of fear away from you. Do not fear, Mary; for you have found grace with God (Luke 1:30). Do not judge grace by the measure of nature; for grace does not allow itself to be made subject to the laws of nature.
Latin
Haec dum intra se cogitaret sanctissima Virgo, talibus Archangelus sermonibus disceptationem eius solvit, dicens ad ipsam: Spiritus Sanctus superveniet in te, et virtus Altissimi obumbrabit tibi. Ideo et quod nascetur ex te sanctum, vocabitur Filius Dei. Et ne timeas Maria: non enim ut metum tibi incuterem, adveni; sed ut metus materiam a te repellerem. Ne timeas Maria: invenisti enim gratiam apud Deum. Ne diiudices gratiam secundum naturam. Legibus enim naturae, se subiici gratia non patitur.