Lina Medina was just five years old when she gave birth to a baby boy in 1939.

Her mother noticed Lina’s stomach growing after she complained about abdomen pains, and initially doctors believed she was suffering from a large tumour.

But the truth was even more frightening and bizarre.

Just weeks later on May 14, 1939, Lina gave birth to a baby boy via a c-section, as her young pelvis was too small for a natural birth.

Lina Medina, the youngest confirmed mother in medical history https://t.co/HsyFhxJjCY pic.twitter.com/hkGxT1fAMR

— Old Pics Archive (@oldpicsarchive) January 29, 2017

She named her baby Gerardo, after the doctor who delivered him. Gerardo was born a healthy 6lbs and would go on to live until he was 40 years old.

When Gerardo was born, the doctor discovered that despite Lina only being five years old, she had mature sexual organs and suffered from a condition called precocious puberty.

According to the Mayo Clinic, precocious puberty is when a child’s body begins changing into that of an adult (puberty) too soon. Puberty that begins before age 8 in girls and before age 9 in boys is considered precocious puberty.

Lina Medina, a most disturbing story.

In 1939, FIVE-yr-old Peruvian girl Lina gave birth 2 a healthy baby boy. A medical miracle#amwriting pic.twitter.com/mlqXm6Y619

— Enricoh Alfonzo (@Alfonzowords) February 1, 2017

It was believed that Lina was a victim of incest at the hands of her father and he was arrested. He was later released by police due to a lack of evidence and the true identity of the father has never been revealed to this day.

Until the age of ten, Gerardo believed that Lina was his sister. He died in 1979 from a bone disease.

According to Rare Historical Photos, Lina, who has never spoken about the pregnancy, is still alive today.

How to answer the fraught question: ‘When are you having a baby?’ On Mamamia Out Loud. 

She went on to marry her husband Raul in the 1970s and later gave birth to a second son.

Lina’s case has often been considered a hoax, but doctors say they have x-rays and biopsies that prove she really was pregnant.

And almost 80 years on, Lina is still the youngest person in the world to have ever given birth.