A pregnant woman from Birmingham could face the death penalty in Pakistan for being found in possession of £3.2 million worth of heroin.

Human rights campaigners are concerned for the future of Khadija Shah, 25, who has spent five weeks in custody with her four-year-old daughter and five-year-old son awaiting the start of her trial at a Rawalpindi court.

Shah was arrested at Islamabad airport in May while trying to board a flight to Birmingham. She was carrying multiple suitcases which were filled with a total of 63kg of the drug, split into 123 packets.

Shah, who is six months pregnant, has not been formally charged. She said she was asked to take the bags to the UK as a favour.

Shah told the BBC: "I had no idea what was in [the bag]. I wouldn't do that with two young people."

Clive Stafford Smith, of the legal charity Reprieve, said that the children have both become ill in jail. Pregnant women have died in the prison in which Shah is held, he said.

He told the Telegraph: "Here's a woman who's six months pregnant with two very small children who are already obviously suffering in unhygienic conditions.

"The far greater threat to Khadija and her children is that they are going to die as a result of the unsanitary conditions in that prison than that [she gets] the death penalty."

Executions have not been carried out for drugs convictions in Pakistan since 2008.

Shah will appear in court again on 25 June.