When Mary was born on 25 February last, it was immediately apparent that something was wrong. Her mother, 18year-old Anita, had been through a very hard labour and lost a lot of blood. Her grandmother, also called Mary, was watching on anxiously. "As soon as she was delivered, she was taken away to a resuscitation table, and we knew we were in trouble, " said Mary Cunningham. "At first, the doctors thought she had Edward's Syndrome, which is basically a death sentence. They told us to baptise her the day after she was born because she probably wouldn't live longer than a few days."

But tests soon revealed that baby Mary actually had an extremely rare and terminal form of the genetic disorder Smith-Lemli-Opitz Syndrome (SLOS).

The prognosis was bleak. Mary had holes in her heart, a curved spine, a cleft palate, and an inability to make or absorb cholesterol, making it extremely difficult for her to put on weight or grow. Only one in 60,000 babies with type 2 SLOS even make it to birth. Of those, most die within hours. Mary was given a few weeks to live.

"The doctors are basically winging it, " said Mary Snr. "This syndrome was only discovered around 30 years ago, and there have been so few survivors that really no one knows anything about it. We believe a seven-year-old girl in Canada is the oldest living person with the syndrome. So far, a lot of what the doctors have told us has turned out to be wrong. So we don't know what to believe or what to expect."

As well as predicting a much shorter life span for baby Mary, doctors also said that she would never mentally develop beyond three weeks old.

"They said she wouldn't recognise us, or smile or laugh, or form a personality, " said Mary. "But they were so wrong about that. Mary knows us. She smiles and tries to sing when we have music on. She babbles away, and thinks she's making sense. She's got a fantastic little personality already."

For now, Mary's family count every day as a blessing. "I'm just so happy that I've got to know her, " said Anita, Mary's mother. "It makes it harder in a way, because it will be much more difficult to say goodbye. But I wouldn't have given up this chance for anything."

If Mary gains enough weight, Anita hopes to bring her to the US for treatment.

Until then, she is reliant on help from the Jack and Jill Foundation and Our Lady of Lourdes Hospital in Drogheda. A fund has also been set up to raise money for her treatment. All donations can be made to Bank of Ireland Drogheda, a/c 46215672, sort code 903322.