A pregnant woman convicted of drug smuggling in Laos says she was saved from the death penalty by becoming pregnant by a fellow British prisoner, according to reports.

Samantha Orobator, 20, was sentenced to life in prison last week after being caught with 1.5lb (680g) of heroin at Wattay airport in the capital Vientiane.

She told authorities that John Watson, 47, who is also serving a life sentence in Laos for drug smuggling after being detained in December 2003, is the father, according to The Observer.

Nigerian-born Orobator, of south London, told the Lao authorities she impregnated herself by a fellow prisoner in an effort to escape the death sentence as Lao law forbids the execution of pregnant prisoners.

Watson's mother Pat, of Halifax, West Yorkshire, told the newspaper her son had asked her how she felt about becoming a grandmother when he told her about Orobator a few months ago in an email.

"At first I thought he was joking, but then he rang me and he sounded ecstatic," she said.

"He told me he'd met a girl and she was having his baby.

"John has been looking after Samantha and they've spent a lot of time together."

She said that men and women were held in separate cells in the jail but mixed in the yard and other areas of the prison.

Foreign Secretary David Miliband signed a prisoner transfer agreement with the government of Laos last month which could lead to Orobator being transferred to the UK to serve her sentence.