A normal birth is simply the culmination of the initial incarnation that was Mary becoming pregnant. There is no logical justification for a miraculous birth. In fact, it shows that the virgin pregnancy was not needed and simply an arbitrary happening.
No, the conception and Incarnation were supernatural, miraculous events. The reuslting pregnancy was a miracle. It does not follow any logic to claim that His birth must have been "natural." At which point did His existence in Mary cease to be a miracle and just an "ordinary" event to warrant an ordinary" Birth?