“Don’t greet Mama Mary ‘Happy birthday!’”
That’s a Facebook post by a friend who is also a Roman Catholic apologist (defender). He posted it before “The Feast of the Immaculate Conception,” a Catholic feast celebrated every December 8. He was concerned that it actually shows the ignorance of some Catholics as far as their beliefs are concerned.
It was not without basis.
The feast was not about the birth of the Blessed Mary, the mother of our Lord Jesus Christ. It was about her miraculous conception in the womb of her mother. Unlike the Lord, she was not virgin-born. But even if she was conceived by a human father and a human mother, the supposed miracle as far as the blessed Mary was concerned is that she was conceived (and born) without sin.
In the Constitution Ineffabilis Deus of 8 December, 1854, Pius IX pronounced and defined that the Blessed Virgin Mary “in the first instance of her conception, by a singular privilege and grace granted by God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved exempt from all stain of original sin.” 
Note that it was only in the 19th century that the doctrine was pronounced and defined. There is actually a debate as to whether the church fathers (those who succeeded the apostles) believed it.
…it appears that the belief in Mary’s immunity from sin in her conception was prevalent amongst the Fathers, especially those of the Greek Church. The rhetorical character, however, of many of these and similar passages prevents us from laying too much stress on them, and interpreting them in a strictly literal sense. The Greek Fathers never formally or explicitly discussed the question of the Immaculate Conception. 
The writings of these church fathers about this topic are subject to different interpretations. So, we cannot really use their writings as a basis. Though we may learn from them, they were not infallible.
What about the Bible? The Online Catholic Encyclopedia directly admitted that, “No direct or categorical and stringent proof of the dogma can be brought forward from Scripture.”  Simply put, this doctrine is not taught in the Bible.
Let me quote a passage from a Catholic Bible, “All scripture is inspired by God and is useful for teaching, for refutation, for correction, and for training in righteousness, so that one who belongs to God may be competent, equipped for every good work.” (2 Timothy 3:16-17, New American Bible Revised Edition) We Bible believers hold on to the sufficiency of the Scriptures. In the Greek, the word “competent” means “thorough, complete, capable, proficient, able to meet all demands.”  It also equips us for “every” work. That means everything we need for faith and practice, for what to believe and what to do, is in the Bible.
The Bible also declared that, “for all have sinned and fall short of the glory of God” (Romans 3:23, ESV). “All” means everyone and excludes no one with the Lord Jesus as the only exception. That truth is directly, categorically and stringently taught by the Scripture and even by the early church fathers.
For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God. (2 Corinthians 5:21, emphasis added)
For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin. (Hebrews 4:15, emphasis added)
That’s why we see no biblical reason to hold on to this Catholic dogma or teaching of the immaculate conception.
Brothers and sisters, let us know what and why we believe.
 “Immaculate Conception,” Catholic Online, http://www.catholic.org/encyclopedia/view.php?id=6056, accessed December 10, 2016. Emphasis added.
 Ibid, emphasis added.
 “ἄρτιος,” Bill Mounce, https://billmounce.com/greek-dictionary/artios, accessed December 10, 2016.