(Cover) - EN Showbiz - Sienna Miller has been "nesting" ahead of her looming labour date.

The British actress and her beau Tom Sturridge are currently expecting their first child. Sienna can't wait to become a mother and sources say the star is mentally preparing herself before her due date in July.

"Sienna is counting down the days to the birth. She's been nesting and spending lots of time with her sister Savannah's four children," a source told UK magazine Closer.

Sienna, 30, is embracing her ever-changing body. The stunning star is said to be indulging in a variety of treats and isn't too bothered about the consequences.

"Sienna's craving sweet treats, such as Maltesers, brownies, tarts and cakes," the insider revealed. "While she's not gained too much weight, she is enjoying her curvier cleavage!"

Sienna and Tom are believed to be engaged. They started dating in mid-2011 following her split from actor Jude Law. (C) Cover Media