Jessica Simpson has confirmed she's pregnant with her second child in a sweet Christmas Day tweet.

After weeks of speculation suggesting the singer-turned-fashion mogul and reality TV star was expecting again, Simpson made the baby news official 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'.

Little Maxwell was born in May, just before her famous mom signed up to front a lucrative new diet campaign for WeightWatchers.

It doesn't seem as if WeightWatchers bosses are too concerned that their new spokesmodel is set to gain back the weight she lost after first becoming a mum - they sent out a Christmas Day tweet congratulating the singer and her husband-to-be Eric Johnson, adding, "Your WW family is so thrilled for you. What an amazing year you've had!"