It's miraculous.... at least it was in the King of Tars

In Christianity miracles are seen to be these glorious gifts from God, and let's all just admit it that in The King of Tars, when that baby was born they surely needed something.
The baby that was born in the King of Tars was this lump, (still unsure what it would look like but I'm going with this fleshy little ball that if you dropped it and a hill was around, it'd probably roll.) and the sultan and the princess decided to have this pray off to see whose God would come through and make their baby a human.

King of Tars, Sultan praying to the idols.

Deformities were seen to be the fault of the mother, who while pregnant had dreams that contained sexual thoughts that were impure, that they were sexually active with multiple partners, or that they were into witchcraft and were in cahoots with the devil. Children born with deformities were called "Changelings" and that they were human children switched with the Devil's substitutes because the mother either slept with Satan or both parents were into the black magic. In our story the issue could be seen is we have two different religions coming together, Christianity and Paganism. The Princess is visited by Jesus in a dream and saved from a demonic hunt and is reassured in her faith that she pretends to convert and keeps her Christian religion as her true religion in her heart. So she sleeps with the Sultan who isn't Christian and their blood mixes and well the outcome is less than desirable.
So the Sultan prays to his idols and Gods to help his son and nothing happens and he gets angry and breaks the idols. The Princess has a priest come and he baptizes the baby and the next thing we know boom a miracle. The baby has flesh, a face and limbs. We have a real life baby. The miracle gives the Sultan and the Princess a child and convinces the Sultan to forsake his religion and convert to Christianity, which for the Princess is a miracle in itself.
The actual transformation of the child is a divine vision of the miracle performed and is often used to bring the reader in and used for conversion purposes. It takes things that are seen as monstrous and dangerous and through faith and God brings it to something that is miraculous.
When looking to the miracle it also seems to protect the protagonist because the baby links her to witchcraft and evil entities with the devil and by the miracle she's able to turn it to good and use it towards her cause of not only converting others to Christianity but saving her child and in the end her husband. 

Work Cited: Magic and the Supernatural in Medieval English Romance Corinne Saunders