Sienna Miller reportedly revealed she has "grown up overnight" since becoming pregnant.

The actress is expecting her first child with boyfriend Tom Sturridge, who she has been dating for a nearly a year.

Sienna is known for her love of partying and famously had an affair with married actor Balthazar Getty three years ago. However, the stunning star is said to have calmed down since meeting Tom and becoming pregnant.

"Sienna used to love partying, but now she's yawning by 11pm if she goes out!" a source told British magazine Closer.

"She's told friends she's grown up overnight and all she thinks and talks about now is buying a new house, decorating and baby stuff."

The stunning 30-year-old star has been spotted out and about looking healthy and happy. Sienna is said to be feeling great.

"Sienna's glowing. She hasn't put on too much weight anywhere else, so she's got a gorgeous neat bump," the source added.