Spanish twins born in 1 in 80,000 rare 'mermaid birth'

A pair of Spanish twins has reportedly been born in a phenomenal event occurring in less than one out of every 80,000 births.

The twins were delivered in a 'mermaid birth' which occurs when the amniotic sac does not burst during labour and the babies are contained within it upon delivery. It is also referred to as a 'veiled' or 'en caul' birth.

Spanish doctor Ana Teijelo shared photos and videos of the incredible delivery on Twitter.

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"The first veiled cesarean section I've seen and I loved it, and I'm not telling the students anything (although I admit that I'm the one screaming)," she wrote alongside the images.

According to Healthline, the sac has two layers and is filled with amniotic fluid which the baby floats in during development, protecting them and keeping them warm. Babies also sometimes drink the fluid, aiding in developing their lungs, stomach, intestines, muscles, and bones, and even helps them excrete for the first time after birth.

The amniotic sac is usually ruptured at the beginning of labour, signalled by 'water breaking'. This means that mermaid births are less common in vaginal births compared to caesareans, but can still occur, especially if the baby is premature.

In caesarean births, doctors can choose to cut through the sac to give birth, but others, like in this case, decide to deliver the babies fully contained within the sac.

"The twins when they were born were wonderfully well. All the staff have enjoyed the delivery," the doctor wrote in a follow up Tweet, along with a photo of the newborn twins.

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Many congratulated the mother on her rare birth.

"Welcome beautiful baby! Hola!," said one welcoming commenter. "Welcome to the world! God bless you all with a wonderful life," said another.