Vico:
Mary bore her Son without any violation of her virginal integrity.
It is important to note that virginity cannot be observed or reduced to physical traits.
Mary’s virginity is intact by never having relations with any man, and enhanced by practicing perfect chastity during her earthly life. Like Christ bore scars from his execution on the Cross, Mary may well have bore stretch marks or other physical scars of child birth. None would effect her virginity in any manner.
None of the Evangelists felt it was necessary to the faith to elaborate on Mary’s process of giving birth. St. Luke, a physician who spoke in detail about the physical aspects of Christ’s miraculous healings, simply said that Mary had given birth. Nothing more than this is necessary for the faith. If there were more to say about the birth, he would have elaborated.
The fact of the virgin birth is a historical reality documented by the early apostles; it is not something that could be derived philosophically from natural law, as it is a miraculous exception to natural law. The church has confirmed infallibly that virgin birth is consistent with the faith and indeed the most fitting and proper manner that Christ could become incarnate, but our knowledge of it comes from the testament of those who knew Mary during her earthy lifetime. Anything more about the exact mode of that birth are historical details the church has no authority to speak on.