Pregnant star JESSICA SIMPSON has debuted her bulging baby bump on Twitter.com, less than a week after announcing she is expecting her second child.

The singer/actress confirmed weeks of speculation on Christmas Day (25Dec12) by posting a photo of her seven-month-old daughter Maxwell sitting in the sand during a festive vacation in Hawaii behind the message 'BIG SIS'.

Now Simpson, who is engaged to Maxwell's father Eric Johnson, has returned to the microblogging site to share a photograph of her growing belly.

The star, who is wearing a bikini and long, flowing floral shirt in the snap, declared on Sunday (30Dec12), "Bumpin' and proud!"