The statement is problematic as it reads like an established fact when the Church has no official teaching on the physiological.aspects of Jesus’ birth. What the Church does teach is that "Mary bore her Son without any violation of her virginal integrity" (De fide on the ground of the general promulgation of doctrine).
Ludwig Ott, in his book Fundamentals of Catholic Dogma, explains that "The dogma merely asserts the fact of the continuance of Mary’s physical virginity without determining more closely how this is to be physiologically explained" (205). However, he goes on to say that in general, "the Fathers and Schoolmen conceived it as non-injury to the hymen, and accordingly taught that Mary gave birth in miraculous fashion without opening of the womb and injury to the hymen, and consequently also without pains" (cf. Summa Theologiae III:28:2). For further reading on this subject, see The Virgin Birth and the Birth of Science by Stanley Jaki.