Bernard would seem to have been speaking of conception in the active sense of the mother's cooperation, for in his argument he says: "How can there be absence of sin where there is concupiscence (libido)?" and stronger expressions follow, showing that he is speaking of the mother and not of the child.
What did the query starter believe to be the ultimate difficulty in accepting  the a virgin conception of Mary ?
How can there be absence of sin where there is concupiscence (libido)?