Sienna Miller, 30, gave birth to her first child with fiance Tom Sturridge, 26, over the weekend in London, Us Weekly reports.
Details on the baby's gender, name and weight have not yet been reported.
Miller briefly discussed her pregnancy with Vogue U.K. in the magazine's March issue. "I'm in my second trimester, so I'm I-can-talk-about-it pregnant," she said. "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."
More stars who are expecting babies in 2012:
Jessica announced that <a href="http://www.huffingtonpost.com/2012/12/25/jessica-simpson-pregnant-baby-maxwell-photo_n_2362558.html">she's expecting her second baby</a> on Christmas. She and fiance Eric Johnson have a seven-month-old daughter Maxwell.
The Duchess of Cambridge is <em>officially</em> expecting her first child with Prince William! The mom-to-be is <a href="http://www.huffingtonpost.com/2012/12/03/hyperemesis-gravidarum-kate-middleton-pregnant_n_2234099.html">suffering from Hyperemesis Gravidarium</a>, a rare maternity condition which brings on severe nausea, vomiting, weight loss, dehydration, lightheadedness and fainting.
Fergie & Josh Duhamel
The couple announced their baby news on Twitter Feb. 18, after weeks of speculation.
The actress is expecting her second child with husband Javier Bardem. The couple already has a 2-year-old son Leo.
Evan Rachel Wood
The actress is <a href="http://www.huffingtonpost.com/2013/01/11/evan-rachel-wood-pregnant-jamie-bell_n_2456954.html">expecting a baby</a> with her new husband Jamie Bell.
CaCee Cobb & Donald Faison
Jessica Simpson's best friend Cacee Cobb and new husband Donald Faison are expecting their first child together. The couple of six years married in December in the backyard of Faison’s "Scrubs" co-star Zach Braff.
The actor and comedian and his model fiancée Megan Wollover are expecting their first child together early this summer.
Berry is expecting her first child -- a boy -- with fiance Olivier Martinez. She is already the proud mommy of 5-year-old daughter, Nahla.
Sigler and her brand new fiance Cutter Dykstra are expecting their first child together.
Hilaria & Alec Baldwin
The couple announced that <a href="http://celebritybabies.people.com/2013/02/12/alec-baldwin-hilaria-baldwin-pregnant-expecting-baby/">they're expecting their first child</a> together. Alec already has a 17-year-old daughter, Ireland, with ex Kim Basinger.
Mario Lopez & Courtney Mazza
The newlyweds are expecting their second child, Mario revealed. “I am the happiest father in the world," <a href="http://www.extratv.com/2013/02/19/mario-and-courtney-lopez-expecting-baby-no-2/">he told Extra</a>. "We cannot wait to welcome baby Lopez number two into our lives.”
The "Saved by the Bell" star and his wife Catriona McGinn are expecting their first child together this September. Gosselaar is already a dad to two kids -- son Michael, 9, and daughter Ava, 6 -- with ex-wife Lisa Ann Russell.
Jamie Anne and Marshall Allman
"The Killing" star and the "True Blood" actor are expecting twins in the spring of 2013.
The "Cougar Town" star is <a href="http://www.huffingtonpost.com/2012/12/10/busy-philipps-pregnant-cougar-town-star-expecting-second-child_n_2272754.html">expecting her second child</a> with husband Marc Silverstein.
According to Us Weekly, Heather Morris, 26, and longtime beau Taylor Hubbell are expecting their first child.
Trump and her husband Jared Kushner <a href="http://www.huffingtonpost.com/2013/04/11/ivanka-trump-pregnant-second_n_3060630.html?utm_hp_ref=celebrity" target="_blank">are expecting their second child</a> this fall.
Wright and her husband Eric Christian Olsen are expecting a baby boy in August, <a href="http://celebritybabies.people.com/2013/04/17/eric-christian-olsen-expecting-son/" target="_blank">People confirms</a>.
Vince Vaughn's wife <a href="http://www.huffingtonpost.com/2013/04/27/vince-vaughn-baby-actor-wife_n_3169237.html?utm_hp_ref=celebrity" target="_blank">is expecting the couple's second child</a> in August. The pair already has a daughter Locklyn.
The "Hart of Dixie" star is expecting her first child with husband Kyle Newman.
Rachel Leigh Cook
The "She's All That" star and her husband Daniel Gillies are expecting their first child this fall.
Monica is expecting her first child with husband Shannon Brown, but she's already mom to sons Rocko, who turns 8 later this month, and Romelo Montez, 5.
The actress is expecting her second child.
Jennifer Love Hewitt
The "Client List" actress and her boyfriend, Brian Hallisay, are expecting a baby.
Winslet and her husband Ned Rocknroll are expecting their first child together.
The "Real Housewife" is expecting her third child with husband Kroy Biermann.
The "Arrow" star and his wife Cassandra Jean are expecting their first child together.