The extraordinary moment when a newborn baby moves his head around while encased in his mother's amniotic sac after a C-section has been caught on camera.

The astonishing video, which was taken in Istanbul, shows the boy's face making expressions within the liquid-filled protective membrane only moments after being pulled from his mother's abdomen.

There's only a one-in-80,000 chance of an 'en caul' birth – during which the infant remains inside the amniotic sac after delivery – and the phenomenon is even rarer during C-sections.

Gynecologist Dr Eray Balcan filmed the event and said: "Welcome, little handsome."

'En caul' is derived from the French translation of 'in caul', with a 'caul' being the amniotic membrane enclosing a foetus inside the mother's womb.

En caul births are less common during caesarean-sections because the doctor's scalpel most often punctures the thin sac.

The amniotic fluid surrounding the baby protects it from hard knocks and also helps to transfer food and water to the embryo as it grows.

The umbilical cord that medical staff later cut provides the main passage for oxygen to reach the foetus from its mother's bloodstream.

The sac usually breaks during a natural birth in a sensational event many know as that gushing moment in Hollywood RomComs where the female partner grabs her man's arm and says: "I think my water just broke."

People who saw the video responded with astonished comments and praise for the doctor's skill in delivering the baby boy.

One wrote: "May we always have such happiness and miracles in our lives. Welcome to our world, and may you always be happy."

Babies only start to breathe by themselves after being born and natural contractions during birth help to squeeze amniotic fluid from their lungs in preparation.

Some C-sections are spontaneous when there are complications during the birth process.

These complications can include risky positioning of the baby within the womb or an incompatible response from the mother's body.