Milagros Cerron's name means "miracles" in Spanish. Born in Peru nine months ago, it is a miracle she is still alive today, for she has sirenomelia, or mermaid syndrome.

From her waist up, Milagros smiles and babbles like any healthy baby. But below the waist, her stomach merges seamlessly into her legs, which are joined all the way to her heels. With her tiny feet splayed in a v-shape, the impression of a mermaid's forked tail is complete.

The condition is about as rare as conjoined twins, but sufferers rarely live for more than a few hours as they lack kidneys or have other complications. Her heart and lungs are fine, although she has only one kidney.

Later this month, Milagros will undergo complicated and risky surgery in Lima in an attempt to separate her legs, which have separate cartilage, bones and blood supplies.

The medical team will be lead by Luis Rubio, who has spent recent months undergoing a crash course in a condition he had read about but never expected to be treating.

The bones of both her legs are visible and move separately, "as if she wanted to get free of this sack," Dr Rubio said. "Her relation to her surroundings is good. She babbles words. She is enchanting and is a wonderful joy."

He took on Milagros' case when she was two days old and is treating her at a charity hospital in a poor area of Lima.

Milagros' father, Ricardo Cerron, 24, appealled for help when she was born on April 27 in the Andean town of Huancayo, around 200 miles (300 km) east of Lima. "I thought it was something horrifying" he said. "I was in total despair."

Milagros, who weighs 17 lbs (7.5 kg) and is 24 inches (60 cm) long, has a rudimentary anus, urethra and genitalia all located together.

During the five-hour procedure, surgeons will insert three silicone bags filled with saline solution between her legs and gradually add liquid to stretch the skin to cover exposed wounds once they are cut apart, centimetre by centimetre.

"I have faith it will all go well," said Milagros' mother, Sara Arauco, 19.

There may only be one other surviving "mermaid" - Tiffany Yorks, a 16-year-old American girl, whose legs were separated when she was a few months old.

Mutaz Habal, the doctor who began treating Tiffany when she was one hour old and helped to pioneer the separation technique, said the procedure was very dangerous. "My only desire is to have another survivor," he said.

Tiffany, who lives in New Port Richey, Florida, walked for six years after her separation surgery but is now wheelchair-bound after an accident.

"We want to dream that she could one day run or ride a bike," Dr Rubio said. "But if we could just give her the ability to be independent, that's enough."

If the operation is a success, the infant will need further surgery in the future to rotate her feet forward and reconstruct her genitalia, he added.

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