The Dublin-based mother of a pregnant woman sentenced to life for drug smuggling in Asia has defended her daughter's explanation that she fell pregnant in prison after injecting herself with a sperm-filled syringe.

Samantha Orobator (20), originally from Nigeria but a naturalised British citizen, was sentenced to life imprisonment earlier this month in Laos for attempting to smuggle 1.5lb of heroin.

The British government signed a prisoner-transfer agreement with Laos so that Orobator can serve her sentence in the UK. However, as she has now entered the third trimester of her pregnancy, she will only be medically fit to travel over the next four weeks at most.

Initially, it was feared Orobator would face the death penalty if found guilty, but Laos law forbids the execution of pregnant prisoners. There has been speculation that she became pregnant in prison to avoid the death penalty.

The explanation she since gave to the prison authorities is that a fellow British prisoner, John Watson (47), also serving a sentence for drug smuggling, is the father of her unborn child through insemination with a syringe.

Her mother Jane (40), a Trinity College Dublin student, was initially concerned that her daughter may have been raped by a prison officer at the all-female Phonthong prison.

But she has since visited her daughter in jail and said Samantha was told she must provide the authorities with an explanation about how she fell pregnant. "It is a matter of privacy [how she fell pregnant]. It doesn't make a difference how it happened. My concern at the moment is to get her back to the UK. Time is not on her side," Ms Orobator told the Sunday Tribune.

"She did what she did [drug smuggling] under duress... The pregnancy is going well and she is okay herself. It was a mixed feeling to see her again. I was so happy to finally see her but sad at the reality of the situation."

A spokeswoman for Reprieve, the British legal charity which sent a representative to Laos in a bid to assist Orobator, said getting Orobator and her unborn child home was now the main priority.

"We don't want to speculate on how she became pregnant. Samantha will be able to tell us when she gets back. She only has a matter of weeks left before she can no longer travel by plane, so getting her home is now our focus," she said.