Fewer than one in 80,000 pregnancies result in what is called an "en caul" birth, meaning the newborn is delivered still encased in its amniotic sac (traditionally known as a "caul") because normally the sac ruptures and releases amniotic fluid (i.e., the mother's "water breaks") well before birth occurs. En caul deliveries are rare enough that some obstetricians may never attend one in their entire careers, though not so rare as to prevent multiple videos of such births from going viral on the Internet.
The example above was shot in the Santa Casa de Misericórdia de Barretos hospital, Sao Paulo, Brazil by a nurse, Giselinha Correa, who posted it to YouTube on 4 August 2016 and on her Facebook page two days later. The New York Times provided this translation of her caption (from the original Portuguese):
“Look what I had the honor of filming in my dear Santa House Mercy,” the nurse, Gih Flor de Lis, wrote, explaining that the newborn was actually one of a set of twins, the first of whom was delivered vaginally.
“We were waiting to stabilize the first baby and the second came softly, in fact, look there that beautiful!!! Historic moment! !!!” she wrote in the post.
Other online videos capturing en caul births include one comprising a series of photographs of an infant born prematurely at 26 weeks at Cedars Sinai Hospital in Los Angeles:
And another of a baby born in Spain who was sliced out of his amniotic sac as a cell phone camera rolled: