Original sentence: The doctrine of the perpetual virginity of Mary, which is believed de fide by the aforementioned religions, states that Mary was a virgin before, during and after giving birth, and so covers much more than the doctrine of her virginal conception of Jesus, often referred to as the virgin birth of Jesus
Edited sentence: The doctrine of the perpetual virginity of Mary, which is believed de fide, i.as a doctrine that is an essential part of the aforementioned faiths and thus is held as having the highest degree of certainty, states that Mary was a virgin before, during and after giving birth, and so covers much more than the doctrine of her virginal conception of Jesus, often referred to as the virgin birth of Jesus