A mom has told of her guilt after her newborn daughter developed cancer in the womb and was forced to undergo grueling chemotherapy at just 14 days old.

Just two weeks after she was born, little Annaleise Sisneros was hooked up to machines and surrounded by up to 20 doctors as she was treated with heavy-duty drugs.

Heartbreakingly, the tiny baby’s hair even fell out — a side-effect of her chemotherapy.

Annaleise, now nearly 9 months old, was diagnosed with acute myeloid leukemia, a blood cancer that's rare in kids, in August of last year.

Doctors initially thought her raised, red rash was allergies, but following blood tests her parents were given the devastating cancer diagnosis.

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It is likely it developed in the womb, her parents said.

“We assumed she developed it in the womb, as she had the bumps when she was born," Brandy Sisneros, the girl's mom, said. "So we are assuming she had it while I was pregnant."

“But [when I was expecting] they didn’t catch anything or see anything out of the ordinary," the 25-year-old from New Mexico said. "They don’t know how she got it. No one knows why it happened… it is just one of those things.”

Annaleise is one of the youngest cancer sufferers in the world, but is now – happily – in remission.

Sisneros said she felt “guilty” for her daughter's diagnosis.

“I blamed myself," she said. "Maybe it was something, a chemical I was using. Once you’re pregnant everything you expose to yourself you expose to a baby.”

The full-time mom, who has two older daughters, Aalyiah and Aubrianna, both six – but not twins – was delighted to fall pregnant with Annaleise.

And when she arrived, weighing 7 pounds, everything seemed mainly normal.

“But there were a couple of spots, like bumps, that were not very concerning,” she said. “Then, about five days afterwards, she got these blisters. They were kind of like chicken pox. They were bruise-colored. And a few of them started coming from underneath the skin to above the skin.”

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Taken to Presbyterian Hospital in Albuquerque, N.M., doctors said it could be “an infection or cancer”.

“The next morning they said it was leukemia and they were trying to figure out what kind,” Sisneros said.

A few days later, in August – when Annaleise was just only days old - she had a Broviac tube fitted. This is a central line catheter which allows for long-term access to blood and for chemotherapy drugs to be fed directly into her.

She was also given blood transfusions to ensure her white blood cell count was low enough for chemotherapy to be effective and safe.

Then, at two weeks old, chemotherapy started.

The treatment was supposed to last for 10 days but on day eight Annaleise became critically ill.

“The dosage was adjusted for her age and weight. She was doing really, really good," Sisneros said. "The chemo was supposed to be 10 days but on her eighth day she went into a critical condition."

“The doctors had to stop the chemo and put her on a breathing tube," she said. "They had to give her loads of medicine. At one point she had 20 machines feeding into her."

“They had to put another line in through the groin area," she said. “There was a risk she would lose her toes or whole leg. She was pumped with so many fluids she was swollen; she was really puffy.”

For around a week she was in a critical condition but Annaleise pulled through and started to recover.

After four more rounds of increasingly high dosages of chemotherapy, further blood tests were taken and in October the family was told the treatment was working and she was in remission.

“Now she is back home and we are so proud of her," Sisneros said. "During chemo, they gave her medicine to keep her comfortable – she wasn’t strong enough to take a bottle. It took a toll on her; you could tell when she wasn’t feeling good."

“She would get her blanket and put it over the head," she said. "But, even during the worst periods, didn’t really cry. She’s a superstar.”

This article first appeared on The Sun.