To believe in a concept such as the "immaculate conception" requires something of the believer.
1. A suspension of your knowledge of the human body and how it functions.
or
2. An ability to accept some sort of "un-natural" mating resulting in the pregnancy of Jesus' mother (Mary?)
Perhaps you can explain away the latter option by ascribing to some sort of "coupling" with "God"?????
I have no idea HOW you can explain away the 1st choice. Hence my spiritual infidelity,