Sienna Miller is expanding her family with boyfriend Oli Green. Miller, 43, was all smiles as she debuted her baby bump at the British Fashion Awards on Monday, December 1, rocking a sheer white strapless Givenchy gown and styling her hair in loose waves. "@siennathing is pregnant!" the official Vogue Magazine Instagram account wrote on Monday. "The star revealed she is expecting her second child at 43 with partner Oli Green at the #BritishFashionAwards this evening, in a @givenchy dress and all.