Love poured in from the couple's famous pals after the news broke, with Kim Kardashian West writing, "We're always here for you and love you guys so much.
Gabrielle Union expressed similar sentiments, commenting, "We love you guys so much and we will be here for whatever yall need. Always."
"I'm so so sorry," Hailey Bieber wrote. "Thinking of you and John, praying for you guys and sending you so much love during this time."
"My heart breaks for you and John," Paris Hilton shared. "I am so sorry for your loss. Sending you and your family so much love. Love you beautiful."
Channing Tatum wrote that he was sending the family "so much love," while his ex, Jenna Dewan, commented that she's sending her "whole heart" to the pair during this time.
Busy Philipps and Alyssa Milano praised Teigen for being brave enough to publicly share her story amid this challenging time.
"I'm so deeply sorry for your immeasurable loss. In awe of your bravery and selflessness in sharing as you have, which is going to help so many women and families," Philipps wrote. "Sending you and your family all the love and light while you grieve."
"Thank you for sharing this," Milano commented. "I'm sending you all the love and strength. I'm so sorry."
Bethenny Frankel noted that "it's impossible to assign words to this pain and tragedy," while Sarah Paulson similarly wrote that "there are no words that sufficiently express the sorrow of this heartbreaking loss."
Olivia Munn wrote that she's "sending all my love," while Rumer Willis simply stated, "I am so sorry for your loss."
"I am so truly sorry," Josh Gad expressed. "My deepest sympathies and prayers are with you, John and the whole family. You are surrounded by love and light."
"Babe, I'm so sorry," Vanessa Lachey wrote. "Sending you Love & Light."
Kyle Richards shared that she planned to "say a special prayer for Jack," while Dwayne Johnson said that he and his wife are "sending you guys all our love, strength, support, light and manana."
Dove Cameron wrote that her "whole heart is throbbing and aching for this pain," while Sophia Bush said she's "holding your hearts in my heart." Viola Davis sent "a big virtual hug of love, love, love" Teigen and Legend's way.
Selma Blair acknowledged Teigen's grief, writing, "I am so sorry angel momma. I am so sorry. This grief. This grief. It will hold you and the love will break through. I am so sorry. Your family. You. Love you. My deepest sympathies."
Kenan Thompson, Katherine Langford, Skai Jackson, Bobby Berk, Rachel Zoe, Stassi Schroeder, Derek Hough, January Jones, Cara Delevingne, Nicole "Snooki" Polizzi, Jesse Tyler Ferguson, Charlie Puth and others also expressed their sympathies.
Teigen and Legend first revealed they were expecting baby number three in August. In her post on Wednesday, the 34-year-old model wrote that she and her family are in "the kind of deep pain you only hear about."
"We are so grateful for the life we have, for our wonderful babies, Luna and Miles, for all the amazing things we’ve been able to experience. But everyday can’t be full of sunshine," she said in part. "On this darkest of days, we will grieve, we will cry our eyes out. But we will hug and love each other harder and get through it."
Watch the video below to see some of the previous pregnancy complications Teigen suffered.