Doctors in Indonesia said they are planning to separate one-week-old conjoined twin boys but must wait for them to grow strong enough to survive the "complex" surgery.
Doctor Azwan Lubis, of Adam Malik Hospital in Medan, North Sumatra, said Asni I and Asni II were joined at the chest and belly but were still too small for doctors to attempt a separation.
"Each of the twins has innate heart problems. We are monitoring them until their condition is more stable," Lubis told AFP.
He said it might take at least six months before the boys were strong enough to undergo surgery.
"Both weigh 4.5 kilogrammes (9.9 pounds) in total. They must weigh at least 10 kilogrammes for the surgery," he said.
Lubis's team successfully separated conjoined girls in 2005 but he said the boys' case was "more complex".