The prayer in full is found here.

The last line of the first stanza reads:
“you are among the closest imitators of your divinely conceived Son, Jesus.”
Throughout the prayer, Jesus is referred to as the son of Joseph. Previously, we discussed in what sense that is true, and what the limits are. But the prayer also emphasizes the divinity of Christ, and his divine conception (and therefore also His Incarnation). Jesus is the Son of God.

The next stanza reads:
For like John the Baptist, by a special grace from God,
you remained free from all personal sin,
throughout your entire life,
despite being conceived in original sin,
and of all those born in the fallen state, none is greater than you or John.

I believe (as a point of speculative theology) that both Joseph and John the Baptist were given not only a baptism in the womb — this would be a non-formal baptism — but also a special grace throughout life, beginning in the womb, to remain free from all sin. So Joseph and John had original sin wiped away, just as each of us did at our baptism, while they were each in the womb. But another gift kept them free from personal sin, by the prevenient grace of God, throughout their entire lives.

Even so, they were each conceived in original sin, so they were each marred by the wounds of concupiscence. That is why Joseph could err by thinking he should divorce Mary quietly, though certainly he did not suspect her of wrong-doing. And concupiscence is also why John could ask, through his disciples, whether Jesus was the One, or should they wait for another.

So Joseph and John were each given a baptism in the womb, and each remained free from all personal sin. But they each had imperfections, short of sin, which were a result of concupiscence. They were each in the fallen state, and so each was also subject to disease, injury, and eventually death.

Ronald L. Conte Jr.