On the 8th of December we will celebrate the feast day of the immaculate conception.
Some people mistakenly believe that this refers to the incarnation or the virgin birth; it does not, rather, the immaculate conception teaches:
“The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Saviour of the human race, preserved immune from all stain of original sin.” – Pope Pius IX, [Ineffabilis Deus: DS 2803 (A.D. 1854)].
You might be thinking, if the dogma of the immaculate conception was not defined until 1854, does that mean that it wasn’t believed since the time of the apostles? Was it perhaps an invention of the Middle Ages and then eventually declared a dogma? The answer to both questions is no.
The Church usually defines a doctrine of the faith when that doctrine is in dispute.
Thus the divinity of Christ was defined at the council of Nicea (A.D 325) in response to the Arian heresy; the divinity of the Holy Spirit was defined at the first council of Constantinople in (A.D. 381) in response to the followers of Macedonius; the Canon of Scripture was not infallibly defined until the council of Trent (A.D 1545-1563)  in response to the the errors taught by Martin Luther and the reformers.
In none of these cases was the Church “inventing” doctrine that was previously unheard of or not accepted by orthodox Christians; and so it is with the Immaculate Conception of Mary.
The Early Christians Said What?
Rather than diving into a mountain of Scriptural support for the immaculate conception  I wanted to show you that the belief in the immaculate conception was indeed believed by the early Church:
This Virgin Mother of the Only-begotten of God is called Mary, worthy of God,
immaculate of the immaculate, one of the one.
– Origen (Hom. i in diversa [A.D. 244]).
“You alone and your Mother are more beautiful than any others; For there is
no blemish in you, nor any stains upon your Mother.”
– St. Ephraim [Nisibene Hymns 27, 8 (c. A.D. 379)].
“We must except the holy Virgin Mary, concerning whom I wish to raise no
question when it touches the subject of sins, out of honor to the Lord.”
– St. Augustine of Hippo [Nature and Grace 36:42 (A.D. 415)].
Mary Immaculate, pray for us.
 An argument can be made that the canon of Scripture was defined infallibly prior to Trent at the council of Florence (A.D.1431-1439).