ISLAMABAD, Pakistan — A British woman, held in Pakistan on charges of drug smuggling, has been sent back to prison with her newborn daughter after giving birth in a hospital, a British legal group said Sunday.

Khadija Shah, 25, is being held on charges of trying to smuggle heroin worth nearly $5 million onto a flight to Britain.

She gave birth to her baby girl Malaika a few weeks ago but was returned from hospital to Adiala prison near the capital Islamabad. The birth was not reported until Sunday.

The baby has had no immunizations and has already had to be hospitalized when she developed severe diarrhea in the unsanitary prison, said British legal group Reprieve.

"To keep a baby behind bars is truly barbaric. Baby Malaika is weak and suffering from terrible health problems while Khadija faces execution. No mother would wish this scenario on their worst enemy," Reprieve investigator Sultana Noon said in a statement.

Shah has two other young children. After a period of incarceration when their mother was arrested in May this year, they were freed into the care of a relative.

Mothers are frequently imprisoned with their children while their cases are heard in Pakistan's congested legal system. Criminal cases can take years to complete.