Angelina Jolie and Brad Pitt are allegedly rowing over their sick daughter.The A-list couple - who are in Namibia awaiting the birth of their first biological child together - were worried sick after Angelina's adopted daughter Zahara was struck down with a mystery illness.The 16-month-old tot reportedly stopped sleeping properly and cries when she is put on her back.According to a report in Britain's The Sun newspaper, Brad wants to take Zahara to the US for treatment but heavily-pregnant Angelina wants to stay in Africa until she delivers her baby.A source said: "Brad is absolutely beside himself. He's desperate to take Zahara to the US for medical attention. But Angie insists on staying in Africa."It has caused a number of fights between them."It's thought Zahara may have a genetic illness, but a number of tests have failed to provide any clues.

The source added: "She's had so many tests, but no one knows what is wrong."

Meanwhile, Brad and Angelina, who also has an adopted son, four-year-old Maddox, have reportedly sold the first picture of their unborn baby for a staggering

£2.6million.

The pair allegedly negotiated the huge fee, which will be donated to charity, with an American weekly magazine.