Sienna Miller hit the streets of London to film a commercial for Amore Pacific skin care line today. She covered her baby bump in a striped top for the cameras, and ducked into a van for touch-ups in between takes. Sienna's expecting her first child with her rumored fiancé Tom Sturridge and the couple were spotted showing PDA in NYC earlier this month. They've kept pretty quiet on their upcoming addition, but Sienna did share her excitement about the baby in an article for Vogue UK's April issue. There's another project on the horizon for the duo, since Tom has On the Road coming out later this year. The first On the Road trailer was released this month, and features Tom as well as his costars Kristen Stewart and Garrett Hedlund.