Miller's sister confirms baby niece's name in Tweet

Sienna Miller (Getty Images)

Sienna Miller's sister has set the rumour mill running with a stray tweet that seems to reveal the name of the star's daughter.

The Layer Cake actress has spoken briefly about her pregnancy but has not released any details amid reports she gave birth to a girl over the weekend.

The 30-year-old actress and actor fiance Tom Sturridge, 26, confirmed in January they were expecting their first child.

But her sister, Savannah, tweeted this week: "Marlowe I love you.....".

Miller talked about the pregnancy to Vogue in March, revealing: "I'm in my second trimester, so I'm I-can-talk-about-it pregnant, 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."

Miller began dating Sturridge in March 2011 and in February this year she was pictured wearing a diamond ring on her engagement finger, but both parties have refused to confirm the rumoured engagement.

PA