Media playback is unsupported on your device Media caption More and more young children are growing up in orphanages in South Korea, says the BBC Steve Evans

It used to be said that South Korea's biggest export was babies - Korean children, unwanted in their own land, were adopted by loving new parents outside the country, particularly in the United States.

And then the law was changed. The shame of an increasingly affluent and confident country sending its children abroad to find the love denied at home played on the national conscience so foreign adoption was made much harder.

On top of that, rules were tightened so the unwanted children of unwed Korean mothers had to be registered before adoption.

'Didn't dare tell'

The changes were made with good intentions. Adopted children might want to trace their birth parents so registering full details seemed like a helpful measure.

And why should Korea depend on American parenting, particularly as South Korea became prosperous? Didn't it smack of colonialism?

But the good intentions have led to unintended results: South Korean orphanages are now brimming with children who might previously have found a new life in a foreign family.

Image copyright Getty Images Image caption Orphanages are filled with children who are not adopted because of social taboos

Ten years ago, 1,200 Koreans were adopted abroad. Today, it's a tenth of that figure.

The problem is that adoption in Korea is taboo, so the gap left by the fall in foreign adoptions has not been filled by adoptive Korean parents.

Those who do adopt sometimes do it in secret.

When Choi Hyunjin was adopted, her new, adoptive parents kept it secret even from their own close relatives.

The couple sit on their sofa in a high-rise apartment near Seoul and say with one voice: "We didn't even dare tell our own parents because we knew they would disapprove. They would only say 'Why are you bringing up other people's children'?"

But Mr and Mrs Choi persevered and now they are among a band of adoptive parents who testify in meetings and go to schools to preach the worth of the love which adoption brings to estranged and abandoned children.

Familial past

The taboo arises because the importance of blood-lines in Korea is ancient and deep-rooted. Korean Confucianism places great emphasis on ancestors.

Hollee McGinnis, a Korean-American who was herself adopted and who now researches how adoption affects personality in later life, told the BBC: "Family is everything in Korea. Who you are and your character is based on your family so if you do not have information about your family, you might find yourself having barriers in life."

She said these barriers can even extend to a block on employment.

Image copyright AFP Image caption The Korean war left many children without parents

"In Korea, your potential employer can ask for your family registry. Your family registry has all the information about your relatives. If you cannot produce a family registry that might be a reason for them not to hire you.

"When you write a letter applying for a job, in your cover letter in the West we talk about education, our skills, our experiences. In Korea, they talk about your family - what your dad did; what your mum did - so your character is based on your family."

This means that orphans - who cannot explain their familial past - have a hard time of it.

Those involved in adoption over many years are in some despair.

In 1955, an American couple Harry and Bertha Holt moved from Eugene, Oregon and set up an orphanage in South Korea, moved by the plight of orphans after the Korean war, particularly those with black American fathers and Korean mothers who found it particularly hard to be accepted in Korean society.

Six decades on, their daughter, Molly, continues their work. She deplores the effect of the compulsion on women to register their children: "If they do, they can't ever marry because no husband wants to marry a woman who has had a baby. So now, so many babies are being abandoned.

"They used to have two babies abandoned a month before the law came into existence and now they have 25 a month. And those babies can't be adopted overseas. They can only be adopted by Koreans, and Koreans don't like to adopt."

'Blessed with adoption'

One answer would be to persuade more Koreans to adopt. The taboo would go if the stigma on adoption was eased.

Image caption Stephen Morrison has seen his life significantly improved by being adopted

Attempts are made to do this. The Mission to Promote Adoption in Korea was founded by a Korean who was adopted as a teenage and brought up in the United States.

Stephen Morrison spent eight years in an orphanage before his new parents transported him across the Pacific and transformed his life. He now thrives in Los Angeles as an engineer but returns to his old orphanage near Seoul.

"I came into this orphanage when I was six years old and I left when I was fourteen years old, and during that time I experienced a lot of hunger to be loved," he says.

"I was not a really good student but as soon as I was adopted into a family, I felt that immediate sense of care and love. All of a sudden, it was just magical: I started to excel in school and I want to pass on the blessings I got from adoption to other children that need homes."

When he returns to Korea, he meets his old street pals who were not adopted.

They have not thrived: "I grew up with my friends, my buddies and I'm still in contact with them. I feel I was so blessed with adoption. And yet my friends were not given that opportunity."