Raffles Hospital officials said surgeons had discovered the twins’ brains were more closely linked than previously thought, meaning there would be lengthy delays in the operation.

A hospital spokesman said early on Tuesday the twins’ blood pressure was also proving unstable and the medical team had to rectify this problem before progressing any further.

“Because they have been fused together for the past 29 years, their brains are very adherent to each other,” said a hospital spokesman in Singapore, where the unprecedented surgery is taking place.

He was speaking 37 hours after the operation had started.

The 29-year-old twins Laleh and Ladan Bijani, who are joined at the head but have anatomically separate brains, began the life-threatening operation to separate them at midday on Sunday.

Unstable blood pressure

Doctors face at least another 24
hours in surgery

Hospital officials said it was crucial that doctors be able to adequately support the brains and ensure blood circulation is stable.

Officials did not say the complications were a setback for the twins, insisting the surgeons knew there would be unforeseen problems.

The Iranian twins are the first adult twins joined at the head to ever undergo surgery to be separated and doctors have warned the attempt could prove fatal to one of both of them.

The surgery was initially expected to last 48 hours but Monday evening’s complications and delays earlier have pushed the timetable back. The surgery could last up to three or four days.

The hospital said earlier on Monday that unexpected complexities in removing a strip of bone connecting the women’s skulls put back the surgery by six hours behind schedule.