Pop star Britney Spears' sister Jamie-Lynn has revealed that Britney is due to give birth to her baby in September.

There were speculations that Britney was expecting twins but Jamie-Lynn made no reference to that, reports Ananova.com.

There was also no information about the sex of the baby.

On a message posted on the web, Jamie-Lynn said: "We are getting ready for the new baby's arrival in September! I can't wait. I have been shopping so much for the baby and it is not even here yet!"

Britney married Kevin Federline on Sept 18 last year.