Peru's "little mermaid" — the baby born with legs fused from her thighs to her ankles — will undergo delicate surgery Tuesday night to begin repairing her rare birth defect, her doctors said Monday.

　　Milagros Cerron, who celebrated her first birthday April 27, was born with a rare congenital defect known as sirenomelia, or "mermaid syndrome," which occurs in one out of every 70,000 births.

　　Tuesday's will be the first of three operations to separate her legs, which are seamlessly fused all the way to her heels, a statement from her doctors said. The surgery will focus on her ankles and the lower third of her calves, and is expected to last at least four hours.

　　There are only three known cases of children with the affliction alive in the world today, the child's physician, Dr. Luis Rubio, said in a statement.

　　A team of 10 doctors will assist in the surgery, to be performed in Solidarity public hospital in Lima, the statement said.

　　Milagros' parents were not immediately available for comment.

　　In the last three months, doctors have inserted silicone bags filled with saline solution to stretch the skin so it will be able to cover her legs once they are cut apart.

　　Rubio said last month that "frequent, recurring urinary infections" and a low red blood count had slowed her progress ahead of surgery.

　　Milagros — whose name means "miracles" in Spanish — has a deformed left kidney and a very small right one located very low in her body. In addition, her digestive and urinary tracts and her genitals share a single tube.

　　Rubio said Milagros would need up to 15 years of corrective surgeries to reconstruct and repair her sexual, digestive and other internal organs.