- 7News Yahoo!7 (@Y7News) February 24, 2015
Baby Silas Philips was delivered three months premature at the Cedars-Sinai Medical Center in California.
As doctors performed the Caesarean section on his mum, Chelsea, they were astonished to see his amniotic sac was still intact.
Pictures show Silas curled up inside with the placenta and umbilical cord and his tiny hands and a leg clearly visible.
Until the bag was broken, he was still getting oxygen through the placenta.
The amniotic sac is a bag of clear, pale fluid inside the womb in which the unborn baby develops and grows.
The fluid helps to cushion the baby from bumps and injury, as well as providing it with fluids it can breathe and swallow. It also maintains a constant temperature for the baby.
Typically the amniotic sac breaks on its own before or during birth, which is referred to as a mother's 'water breaking'.
During a Caesarean, the surgeon cuts through it to deliver the baby.
Doctors say the chance of the amniotic sac remaining completely intact after birth is 'ultra rare'.
Dr William Binder, who delivered Silas, said: "Even though it sounds cliched, we caught our breath.
"It really felt like a moment of awe... and one that will stick in my moment for some time.
"He was seconds old and still in the water bag, with the placenta and umbilical cord tucked inside."
After taking an amazing photograph, Dr Binder then carefully took Silas out of his amniotic sac and got him breathing.
She told CBS News: "It was definitely like a clear film where you could definitely make out his head and his hair.
"He was kind of in a foetal position and you could see like his arms and his legs curled up.
"It was actually really cool to see. And when I heard that was actually really rare I was like 'oh my gosh you're a special little baby'."
Despite being born at just 26 weeks, Silas is doing so well that doctors hope he will go home within the next month.
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