Angelina Jolie and Brad Pitt are reportedly considering returning to America so adopted daughter ZAHARA can be treated for a mystery illness. The couple - currently in Namibia awaiting the birth of their first biological child together - are concerned about the 16 month old baby's health, because she has stopped sleeping properly and screams when put on her back. A number of tests have failed to provide any clues about the illness. A source tells British newspaper The Sun, "Brad is desperate to take Zahara back to the US for medical attention. But Angelina insists on staying in Africa until their baby is born."