Eva Clarke has been called the miracle baby. By the time of her birth, her mother Anka had endured six years of Nazi rule, had survived three concentration camps and weighed just five stone.

Image caption Eva and Anka: Baby Eva weighed just 3lbs (1.5kg) when she was born

In the late 1930s, Anka Bergman was a lively law student living in the Czech capital Prague.

"I wanted company and boyfriends and to enjoy myself. I didn't know that Hitler was coming, but I filled my time with only cinemas and theatres and concerts and parties," she says.

It was at a nightclub that Anka met her husband, Bernd Nathan, an attractive German-Jewish architect who had fled Germany in 1933.

"He thought that it was far enough to be safe," said Eva. "It wasn't but, if he hadn't come to Prague, he wouldn't have met my mother."

In March 1939, the Nazis invaded Prague and, from that moment Anka's life, and Bernd's, changed forever.

Secret pregnancy

Anka and her entire family were sent to Terezin (also know as Theresienstadt), a transit camp for the Auschwitz death camp.

Image caption Eva's father was killed before his daughter was born

Anka and her husband Bernd were to remain there for the next three years.

Although the sexes were segregated, Anka managed to meet secretly with her husband and she became pregnant.

"My mother stayed in the same barracks as I did," said Anka.

"And she looked at me: 'How? And where?' She laughed actually, because - in all that misery there - she had a sense of humour."

But as Anka soon discovered, to be Jewish and become pregnant under Nazi rule was a serious offence.

"There were five couples in the same position and we had to sign a paper that the babies, when they are born, will be taken away.

"That's the first time I heard the word 'euthanasia'. But we did sign it."

Anka gave birth to a baby boy. He was not taken away, but he died in the camp from pneumonia when he was two months old.

Chimneys

In October 1944, Anka became pregnant again - but before she was able to tell her husband, he was sent to Auschwitz.

Image caption Eva and Anka Clarke now live together in Cambridge

Astonishingly, Anka volunteered to follow him and was transported to Auschwitz the following day. However, she never saw Bernd again. She later found out that he was shot dead in the camp on 18 January 1945.

It was at Auschwitz that Anka came to understand the true horror of the Nazis' actions.

"We saw the chimneys spouting the smoke and fire and the smell. And it looked like hell," she says.

She herself was lucky to survive more than a few hours there.

"Had my mother arrived in the Auschwitz-Birkenau death camp holding my brother in her arms, she would have been sent straight to the gas chambers," Eva says.

"But because she arrived in Auschwitz not holding a baby, and although she was pregnant again - this time with me - nobody knew, so she lived to see another day."

As Eva puts it, she owes her life to her brother: "His death meant my life, which is a very strange thing to say."

Anka was selected for hard labour working in an armaments factory. Food was scarce and for the next six months she slowly starved.

Then, in April 1945, in the dying days of the war, she was caught up in the Nazi attempt to get rid of all living witnesses to the Holocaust. She endured a torturous three-week train journey.

"It was open to the skies and it was filthy, with no food and hardly any water," she says.

Liberation

On 29 April 1945, Anka arrived at Mauthausen death camp.

The sight of the name Mauthausen at the station was a deep shock to her, as she had heard of the camp's awful reputation early on in the war.

She always says that nobody knows what they can withstand until they have to Eva Clarke

"She says the shock was so great that she thinks it provoked the onset of her labour and she started to give birth to me on that coal truck," Eva says.

"There are two reasons why we survived, and the first is that, on 28 April 1945, the Nazis had dismantled the gas chamber in Mauthausen.

"Well, my birthday is the 29th so presumably - had my mother arrived on the 26th or 27th - I wouldn't be sitting here today.

"And the second reason we survived was because, a few days after my birth, the American army liberated the camp. My mother reckons she wouldn't have lasted much longer."

After the war, Anka remarried and in 1948 - when the communists took over Czechoslovakia - the family moved to Cardiff.

Today she lives in Cambridge with Eva, who is now retired and spends her time visiting schools, telling pupils the story of how she came into the world.

For her it is important to commemorate all the victims of the Holocaust.

"To remember all those thousands and thousands and thousands of people who died, who were killed in the Holocaust, and especially all those thousands of people who've never ever had one single person remember them because all their families were killed," she says.

And she has a huge amount of admiration for her mother: "I can hardly believe that she actually did go through it. But, you know, she always says that nobody knows what they can withstand until they have to.

"And fortunately most of us are not put to the test."

Anka and Eva tell their full story in The Baby Born In A Concentration Camp on Tuesday 19 April at 2235 BST on BBC One. The programme will also be available on the BBC iPlayer.