Excerpted from my booklet:
The Virginity of Jesus and Mary
Some persons claim that the Birth of Christ took place mostly in the usual way, but with a miracle merely to preserve the physical sign of virginity. On the contrary, true perfect virginity must completely encompass and permeate the manner of conception and birth. Perfect virginity is not merely the absence of sexual experience, nor is it merely a physical state. True perfect virginity encompasses the whole person, body and soul, throughout their entire life…. perfect virginity must necessarily encompass the whole person, even from the very first moment of existence, even in the very means of bringing that person into existence. For this reason, Christ and Mary must each have been conceived and born solely and entirely by a miracle of God.
The birth of Jesus Christ occurred solely and entirely by a miracle of God, and not in the usual way. When Jesus was born, He went from His mother Mary’s womb to the outside world immediately and directly by a miracle of God, without any part whatsoever of the usual process of delivery. First He was in the womb, then He was out of the womb, without having to travel through any places in-between. God alone could bring about such a virginal and miraculous birth. The Virgin Births of both Jesus and Mary occurred solely, entirely, and necessarily by means of a miracle of God, and not in the usual way.
Blessed Anne Catherine Emmerich
The visions given to Blessed Anne Catherine Emmerich by God also confirm that the birth of Jesus Christ was entirely virginal and miraculous.
“Joseph suggested to the Blessed Virgin that he should summon to her assistance some pious women whom he knew in Bethlehem. She declined, however, saying that she needed no human help.”
“I saw the radiance round the Blessed Virgin ever growing greater…. At midnight she was wrapt in an ecstasy of prayer. I saw her lifted from the earth, so that I saw the ground beneath her. Her hands were crossed on her breast. The radiance about her increased…. Then I no longer saw the roof of the cave; a pathway of light opened above Mary, rising with ever-increasing glory towards the height of heaven…. Meanwhile the Blessed Virgin, borne up in ecstasy, was now gazing downwards, adoring her God, whose Mother she had become and who lay on the earth before her in the form of a helpless new-born child. I saw our Redeemer as a tiny child, shining with a light that overpowered all the surrounding radiance, and lying on the carpet at the Blessed Virgin’s knees. It seemed to me as if he were at first quite small and then grew before my eyes. But the movement of the intense radiance was such that I cannot say for certain how I saw it.”
A Theological Argument
The phrase “without loss of her virginity” means that Jesus left the womb of the Virgin Mary solely by a miracle of God and not in the usual way. Jesus went from being inside the womb to being outside the womb solely by means of the power of God. This is what is meant by a virgin birth; other explanations are insufficient and unacceptable. The births of both Jesus and Mary were Virgin Births. God is Truth; whoever loves God will love the truth.
Jesus Christ is perfect in all things, including His Perfect Virginity. God alone is the Father of Jesus Christ. God required the Holy Conception of Jesus Christ to be a miraculous Virgin Conception. Since Christ had a Virgin Conception, He must also have had a Virgin Birth, for the Virginity of Jesus Christ is entirely perfect in every way. The perfect, complete, and all-encompassing Virginity of Jesus Christ extends even to His perfect Virgin Conception and His perfect Virgin Birth. This teaching is trustworthy and true; it cannot be otherwise.
God would not give the perfect-Virgin Jesus Christ a Virgin Conception within the womb of His mother, Mary, without also giving Him a Virgin Birth out of the womb of His mother, Mary. His Holy Conception was virginal and miraculous, therefore His Holy Birth was also virginal and miraculous. Every perfect Virgin must have both a Virgin Conception and a Virgin Birth. Jesus Christ is perfect in Virginity. Therefore, Jesus must have had both a Virgin Conception and a Virgin Birth, for without both His Virginity would not be perfect, complete, and all-encompassing. The Virgin Conception and Virgin Birth are joined by God and cannot be separated.
The Virginity of Jesus Christ, the Son of God, is so perfect, complete, and all-encompassing that even His Holy Conception and His Holy Birth were entirely Virginal, occurring solely and entirely by a miracle of God and not in the usual way.
Mary’s conception and birth
The life of the Virgin Mary is a perfect reflection of the life of Jesus Christ. The Virgin Mary is perfect and is the chosen Mother of God because she is similar to Christ in all things except His Divinity. The lives of Jesus and Mary are joined by God and cannot be separated. God gave a Virgin Conception and Virgin Birth to the perfect-Virgin Jesus Christ. Therefore, God also gave a Virgin Conception and Virgin Birth to His Mother, the perfect-Virgin Mary. God would not give Jesus Christ a Virgin Conception and Virgin Birth without also giving His Holy Mother a Virgin Conception and Virgin Birth. Gods wills that the Virgin Mary be similar to Christ in all things except His Divinity.
The perfect Virginity of Jesus Christ requires that His Mother Mary also be perfect in Virginity. The perfect Virginity of Jesus, the Son of God, brought about the perfect Virginity of Mary, the Mother of God. The perfect Virginity of Mary results from and is dependent upon the perfect Virginity of Jesus. The Virgin Mary is both a perfect Virgin and the perfect Mother. The Virgin Mary was required by God to be free from all sin and all tendency to sin, throughout her entire life, so that she could be the sinless Mother of the sinless Son of God. In the same way, the Virgin Mary was required by God to be entirely perfect in Virginity, throughout her entire life, including her Immaculate Virgin Conception and her holy Virgin Birth, so that she could be the perfect-Virgin Mother of the perfect-Virgin Jesus Christ. This teaching is trustworthy and true; it cannot be otherwise.
[Much more on this subject in my booklet:
The Virginity of Jesus and Mary]
 The Magisterium has infallibly taught that the Virgin Mary gave birth to Jesus virginally, with her physical virginity intact. But the Magisterium has NEVER taught that the virgin birth of Jesus included the full and usual process of delivery, with the sole exception being the mere retention of the sign of virginity. This latter point is often assumed, but without any basis in magisterial teaching.
 A true virgin birth must necessarily exclude any use of the birth canal whatsoever. This condition is necessary, but not sufficient. A true virgin birth must also meet other conditions, especially that the birth be accomplished solely by a miracle of God, and not by means of nature, science, or human intervention. A true virgin birth is not birth in the usual way accompanied or assisted by a miracle. But rather, a true virgin birth must occur solely and completely by a miracle from God. A true virgin birth is birth solely and entirely by means of a miracle-fully miraculous and fully virginal.
 Emmerich, The Life of the Blessed Virgin Mary, p. 193.