The reason Jesus had to be born of a virgin is because he would have inherited Adam’s sin if he had a biological father. Somehow Mary was able to be without the taint of original sin with a biological father but Jesus was not if we believe Catholic theology.
Her prayer pronounces that she was without sin?
BTW, the Immaculate Conception is a fairly recent addition to Catholic doctrine.
The solemn pronouncement of the doctrine of the Immaculate Conception only affirmed what had been contained in Catholic Tradition. The Magnificat is Mary’s prayer of worship and gratitude. My point was that she recognized in it that she was to give birth to her Savior.