Bangkok  - British national Samantha Orobator, who mysteriously managed to get pregnant while serving time in an all-female jail in Vientiane, was scheduled to be sentenced Wednesday for drug trafficking, diplomats said.

"We were notified that the sentencing will happen at 1:30 pm," British embassy spokesman Daniel Painter said by telephone from Vientiane. "We're optimistic that after a few false starts it will go ahead," he said.

Orobator, 20, was arrested while boarding a plane in Vientiane last August with 680 grams of heroin allegedly hidden beneath her clothes.

In Laos, the maximum sentence for drug trafficking is death by firing squad. But under Lao law, a pregnant woman is exempt from capital punishment.

Under a hastily pushed through prisoner-swap agreement between Britain and Laos earlier this year, Orobator is expected to be flown to the UK after her sentencing to serve her jail term there.

Orobator's sentencing has been delayed by an investigation into how she was impregnated in the allegedly all-female Phongthonmg Prison.

On Tuesday, the government-run Vientiane Times suggested that Orobator had secretly impregnated herself with sperm from another prisoner, although details were not available on how such an operation could be performed in a prison.

The government has denied claims that she was raped by a guard.

"Maybe it is a baby from the sky like [the Virgin] Mary," Lao government spokesman Kenthong Nuanthasing said in an interview last month.

Little is known about what led Orobator, a Nigerian-born British citizen described by friends as extremely bright with ambitions to become a doctor, to fly to Thailand and then to Laos where she spent five days before her arrest at Wattaya Airport on August 5 last year. (dpa)