miller051511_01_230.jpgSienna Miller is a brand new mom!

The actress and fiance Tom Sturridge welcomed their first child this weekend in London, a source tells Us Weekly, but details on the baby's gender, name and weight have been kept under wraps.

While Miller has remained quiet about her pregnancy for several months, the blonde stunner finally opened up to British Vogue in April, confessing:

"Even though I'm under strict instructions not to say anything as it would completely defeat the point of everything I've tried to achieve in the last eight years. I'm feeling fine...It's all progressing nicely and it's very exciting."

The couple has yet to announce a wedding date after getting engaged during a post-Christmas trip to Paris last year.