Yes, the teaching of the Immaculate Conception came to fruition during the Middle Ages through the Franciscans. It was something that wasn't always believed by the Church and debated fiercely in the Middle Ages. The Eastern Church never took Mary's sinlessness that far. It believed and still does, that the Virgin Mary---Theotokos was free from all personal sin. This belief is an outgrowth of Augustinian theology, & Scholasticism. Augustine overconcentrated on man's sinfulness (In a way he had to--because he was combating Pelagianism, which the East really didn't have to face---they had their hands full with other Christological heresies). The East believes that if you espouse belief in an Immaculate Conception of the BVM, her humanness is somewhat compromised. These points are still argued between East and West. Actually a Mariology developed in the West that basically took on a life of it's own. I am not saying that RC's have divorced Mary from the saving actions of Christ, but somehow Roman Catholicism has produced a Mary on steroids as compared with Eastern Orthodoxy which gives her great honor and devotion.
If you read the Fathers, in particular St. Ephrem, the Immaculate Conception is the logical conclusion of their teaching on the Panagia.
I suggest you look up Martin Jugie's masterful study: L'immaculee Conception dans l'Ecriture Sainte et dans la tradition orientale, Rome: Officium Libri Catholici, 1952, 489 pp.
The Eastern Orthodox (including Photius and Gregory Palamas) held generally to the belief in the Immaculate Conception of the Blessed Virgin from the ninth century until about the fifteenth. Afterwards, it became a disputed issue until the nineteenth century when the party opposing the doctrine won out.
Let every creature dance for joy. Let all the earth cry out and rejoice with exultation, that the medicine for the primal sorrow has just now sprouted, that, by the great solicitude of God for us, the destruction of the hereditary curse (THS PROGONIKHS ARAS) - in which the whole mortal race had sunk - is made present. And today, a heavenly gift such as this is asked for us, that not only that curse may be removed from us, but also that the whole nature be blessed for us, and that on the one hand that the partition-wall of ancient hatred may be abolished, and that on the other that the love of God be in the midst of men, and peace may rise.
Nicetas David Paphlago, Bishop of the Dadybrians in Paphlagonia (890-900 AD), Oration I - On the Natal Day of Saint Mary, Patrologiae Graecae vol. 105, col. 17B. My translation.