The chart star-turned-designer – who had her fourth child, Harper Seven, last month – is said to be resting and receiving medical attention.
No details of the condition are being released because it is “a private medical issue”.
However Los Angeles-based Mrs Beckham, 37, is still hoping to be able to attend New York fashion week next month to showcase her next collection. A spokeswoman for her said: “She is resting and receiving treatment.”
Mrs Beckham is reported to be suffering from a slipped disc.