The baby news comes just five months after the cookbook author gave birth to her daughter Esti Maxine Stephens.
In a lengthy post on her Instagram on Wednesday, Teigen wrote that she has always wanted four children for "as long as [she] can remember."
She also spoke out about the pregnancy journey with Esti and Wren after losing her son Jack in 2020.
"After losing Jack, I didn't think I'd be able to carry any more babies on my own," she wrote in the post.
In 2022, Teigen opened up about her loss and explained that she had a life-saving abortion, as reported by People.
In her Instagram statement, Teigen says, in 2021, she reached out to a surrogacy agency and inquired about having two "tandem surrogates" to each bring a baby boy and girl. "Twins, kinda?!" she wrote.
However, Teigen soon decided she wanted to try to carry a baby one more time and restarted the in vitro fertilization (IVF) process, which is how she got pregnant with Luna and Miles.
"We did my transfer and were so happy to learn it worked — we were pregnant with our little girl, Esti," Teigen said in her post.
Around the same time, Teigen and Legend met with their surrogate Alexandra, who Teigen describes as "incredible, loving, compassionate."
They got to experience pregnancy at the same time.
"We want to say thank you for this incredible gift you have given us, Alexandra," Teigen continued.
"And we are so happy to tell the world he is here, with a name forever connected to you, Wren Alexander Stephens."
Chrissy Teigen and her surrogate Alexandra. @chrissyteigen | Instagram
Teigen ended the post by paying tribute to her son Jack.
"Our hearts, and our home, are officially full. And to our Jack, we know both their angel kisses are from you."
Many of the couple's celebrity friends shared in the excitement of their new arrival and posted congratulatory messages on Teigen's post.
"Congratulations love, I am so happy for you!!🥰" Paris Hilton wrote.
"Congrats to your incredible family!!!! ❤️❤️❤️❤️❤️❤️" Mandy Moore expressed.
Legend also shared a series of photos on his Instagram page on Wednesday.
In the first photo, Legend is holding both his son Wren and daughter Esti. His son Miles, 5, and daughter Luna, 7, are also posing next to their dad.
The final photo is a solo shot of Wren.
Congrats to the whole family!
