A seven-week-old Dominican girl born with one of the world's rarest birth defects died on Saturday, hours after undergoing a delicate operation to remove an undeveloped second head, the clinic treating her said.
A spokeswoman at the CURE International Centre for Orthopaedic Specialities in Santo Domingo said that Rebeca Martinez had died, but gave no other details.
A team of international doctors said on Friday night that they had successfully completed a day-long operation to remove the second head. But doctors had cautioned that the baby would face a series of risks as she recovered, such as infection or haemorrhaging.
The surgery was led by Dr Jorge Lazareff, director of paediatric neurosurgery at UCLA's Mattel Children's Hospital, and Dominican surgeons Dr Santiago Hazim and Dr Benjamin Rivera.
Lazareff led the surgical team that successfully separated last year Guatemalan twin girls conjoined at the head.
Friday's surgery began in the morning and went on until late in the evening, with a team of surgeons and nurses taking shifts.
Martinez was born in mid-December at a hospital in the Dominican capital with the head of an undeveloped twin attached to the top of her skull, facing upward.
The infant was otherwise healthy but her brain could not develop normally unless the undeveloped head was removed.
The $100,000 operation was free for the parents, Maria Gisela Hiciano and Pablo Martinez, the hospital said.
The baby girl's condition, cranio pagus parasiticus, is so rare that there have only been eight documented cases in the world, and no known previous cases where surgery was attempted to correct it, Hazim told Reuters before the surgery.
Conjoined twins form when an embryo begins to split into identical twins and then stops, leaving them fused. Rarer "parasitic" twins occur when one conjoined twin stops developing in the womb, leaving a smaller, incomplete twin that is dependent on the other.
In Rebeca's case, there was a gap in her skull where the heads were joined, and the blood vessels were intertwined.