For a few months in 1972, the newborn boy, who was found in a stairwell in the northern town of Piteå, was Sweden’s most talked about baby.

The case received major media attention and the police launched an operation to find the parents, but the mystery remained unsolved and the boy was eventually adopted.

The mother, now in her eighties, has finally decided to reveal her secret, shocking her other children who had no idea they had a younger brother.

The woman told local newspaper Piteå-Tidningen (PT) that she could no longer bear keeping her secret to herself and that she now hopes to meet her 42-year-old son before she dies.

“I hope the boy can forgive me,” the unnamed woman said.

When she got pregnant with the boy she already had several children – all with the same man, but he left her for another woman.

“He took his rifle and a bag of clothes and left,” the woman told PT.

She worked nights as a cleaner to make ends meet and never told anyone she was pregnant, not even the father.

She gave birth to the boy by herself on her kitchen couch, wrapped him in a blanket and drove off to work a night shift, bringing the baby with her.

She then found herself driving to Piteå, where she left the baby in a plastic bag in the stairwell of an apartment building where a friend of hers lived.

“Today, I can’t understand that I did it. I was a different person,” she said.

The baby, who was in perfect health, was brought to hospital, then placed in an infants’ orphanage and finally adopted.

“Nobody can understand what it’s been like,” said the woman.

“Now it feels better, like I am 100 kilos lighter. I just hope I can get in touch with him and that his adoptive parents have told him that he was adopted.”

Her other children were shocked when she finally told them her secret. They are now keen to meet their younger brother and have tried to find him, but with no luck so far.

TT/The Local/nr Follow The Local on Twitter