NEW YORK, Aug 5: Two-year-old twins from the Philippines who were born joined at the head have been surgically separated, but the next few days are critical to their survival, doctors said on Thursday.

Over four separate operations that began last October, twins Carl and Clarence Aguirre first had their blood vessels separated. The intricate process culminated with their physical separation on Wednesday in a 12-hour operation.

Surgery to separate conjoined twins often takes place in a single marathon procedure. James Goodrich, Montefiore Medical Center's director of children's neurosurgery and the lead surgeon, said the procedure was complicated since the twins shared large blood vessels that fused their brains.

He said the next two days, doctors will watch for the prospect of infection and other complications and that it will take up to two weeks to assess possible brain damage. "This is an enormously complex case," Goodrich said, adding that during the surgery doctors were reassessing strategy "every 15 minutes." Conjoined twins occur once in every 200,000 live births. -Reuters