Julia Stiles took to Instagram on Nov. 21 to announce that she welcomed her first child in October.
"Strummer Newcomb Cook, born October 20, 2017. Thanks and ever thanks to the extraordinary Doctors, Nurses and staff at Mount Sinai for helping bring this utter joy into our lives. 'Hello, World!'" she captioned a sweet pic of her husband, Preston J. Cook, holding their baby's hand.
Eniko Parrish and Kevin Hart
Eniko Parrish and Kevin Hart welcomed their first child together on Nov. 21. The comedian wrote that his newborn son, Kenzo Kash Hart, was already smiling.
Rose Byrne and Bobby Cannavale
Bobby Cannavale (L) and Rose Byrne welcomed their second child together in November. The two are already parents to son Rocco and Cannavale also has son Jake.
Billy Joel and Alexis Roderick
Billy Joel and Alexis Roderick welcomed their second daughter, Remy Anne, on Oct. 22. Joel and his wife also have daughter Della Rose,and Joel has daughter Alexa Ray Joel from his previous marriage to Christie Brinkley.
Spencer Pratt and Heidi Montag
Spencer Pratt and Heidi Montag welcomed their first child on Oct. 1.
Pratt announced the happy news on Twitter, sharing his son's name, Gunner Stone, and retweeting congratulatory messages from family, friends and fans.
Serena Williams and Alexis Ohanian
Serena Williams and Alexis Ohanian welcomed Alexis Olympia Ohanian Jr. on Sept. 1. The tennis icon posted a photo of her daughter on Instagram and shared a video of the story behind the baby's journey. Williams and Ohanian are engaged.
Click through to see more new moms and dads from across Hollywood.
Casey Wilson and David Caspe
Casey Wilson and David Caspe welcomed their second child, Henry Bear Caspe, in late August. Wilson's father said on her podcast Bitch Sesh of the delivery, "Casey was [in labor] and they go, 'OK, push three times and this baby's coming out!' And she goes, 'Wait! Bring me my makeup bag!' So, she put some makeup on so she would be ready."
Jason Statham and Rosie Huntington-Whiteley
Jason Statham and Rosie Huntington-Whiteley welcomed their son Jack Oscar Statham on June 24. The couple are engaged.
George and Amal Clooney
George and Amal Clooney welcomed twins Ella and Alexander Clooney on June 6.
George Clooney's publicist Stan Rosenfield said both are "happy, healthy and doing fine."
Jimmy Kimmel and Molly McNearney
Jimmy Kimmel and his wife, screenwriter Molly McNearney, welcomed a baby boy in April, but Kimmel tearfully explained on his show that his son had a severe heart defect. Billy survived and is doing well, but Kimmel made a plea for affordable health care for parents.
Cheryl Cole and Liam Payne
Pop stars Cheryl Cole and Liam Payne announced on Saturday March 25, the birth of their first child Bear.
Bradley Cooper and Irina Shayk
Bradley Cooper and Irina Shayk reportedly welcomed their baby girl in late March.
Gal Gadot welcomed her second daughter with husband Yaron Versano, making the announcement on March 20.
"And than we were four ... She is here, Maya," the 31-year-old actress wrote on Instagram. "I feel so complete blessed and thankful for all the Wonders in my life."
Tori Spelling and her husband Dean McDermott welcomed their fifth child together on March 2. Spelling announced the news on Twitter with a photo of their newborn holding her finger, which she captioned, "We are so excited to announce the birth of the newest member of the McDermott family!"
Natalie Portman's representative said that she and her husband, Benjamin Millepied, welcomed daughter Amalia on Feb. 22.
Portman was notably absent at the Academy Awards on Sunday, where she was nominated for best actress. This is the second child for Portman and Millepied, who wed in 2012. Their son, Aleph, is 5.
Nick Cannon posted to Instagram that his ex-girlfriend, Brittany Bell, had given birth on Feb. 21 to a baby boy named Golden "Sagon" Cannon, making Cannon a father of three.
Amber Tamblyn and David Cross
Amber Tamblyn and David Cross announced the arrival of their first daughter on Feb. 21.
Hoda Kotb said in an emotional phone interview on the "Today" show in January that she adopted a newborn and named her Haley Joy.
Mel Gibson and Rosalind Ross
Mel Gibson is a father for the ninth time. Girlfriend Rosalind Ross, a writer, gave birth to the couple's son, Lars Gerard Gibson, on Jan. 20.
Maksim Chmerkovskiy and Peta Murgatroyd
Maksim Chmerkovskiy and Peta Murgatroyd welcomed a baby boy on Jan. 4.
"This is, without a doubt, the best thing that has ever happened to us!" the couple said in a statement to ET of their son, Shai Aleksander Chmerkovskiy.
Amy Smart and Carter Oosterhouse
Amy Smart and husband Carter Oosterhouse ended 2016 on a high note by welcoming their first child together.
"It is with great gratitude and pleasure to welcome our little girl Flora to the world," Smart wrote in an Instagram post of the happy family in the hospital in January. "What a blessed way to bring in 2017 Amen and Thank You God for this special new life!!"
Janet Jackson welcomed her first child -- a boy named Eissa -- with husband Wissam Al Mana on Jan. 3.
Pink and Carey Hart
Pink and husband Carey Hart welcomed their second child, a boy named Jameson, on December 26, 2016, the singer announced on Instagram.
"Today" show co-host Savannah Guthrie gave birth to her second child, a baby boy, on Dec. 8, 2016.
Her co-host Matt Lauer said Charles Max Feldman weighed in at a healthy 9 pounds, 8 ounces. Charley, as he will be known, is named after Guthrie's father. The middle name comes from the grandfather of Guthrie's husband, Mike Feldman.
Mick Jagger and his girlfriend Melanie Hamrick welcomed a baby son on Dec. 8, 2016. The child was the eighth for the 73-year-old.
Ashton Kutcher and Mila Kunis
Ashton Kutcher and Mila Kunis welcomed their second child in December 2016.
Kayte Walsh and Kelsey Grammer
Actor Kelsey Grammer and Kayte Walsh welcomed their third child together and Grammer's seventh. The 61-year-old actor's rep confirmed to ET that he and wife Kayte welcomed Auden James Ellis Grammer into the world on Nov. 14, 2016, weighing 7 lbs. and measuring 21 inches long.
Rob Kardashian and Blac Chyna
Rob Kardashian and Blac Chyna welcomed their first child, a daughter named Dream, on Nov. 10, 2016.
DJ Khaled and Nicole Tuck
DJ Khaled and his fiancée Nicole Tuck welcomed a baby boy on Oct. 23, 2016. The social media star and rapper documented the process on Snapchat.
Olivia Wilde revealed on Instagram that she and fiancé Jason Sudeikis welcomed their second child together, Daisy Josephine Sudeikis, on October 11, 2016.
Kerry Washington and Nnamdi Asomugha
Kerry Washington and her husband, former NFL player Nnamdi Asomugha, welcomed a son, Caleb Kalechi Asomugha, on Oct. 5, 2016.
Blake Lively and Ryan Reynolds
Blake Lively gave birth to her second child with Ryan Reynolds at a New York City hospital in late September 2016, a source confirms to ET.
Adam Levine and Behati Prinsloo
Adam Levine and wife Behati Prinsloo welcomed their first child, a daughter named Dusty Rose Levine, on September 21, 2016.