Pauline Chalamet has officially enrolled in mom life.

The Sex Lives of College Girls star gave birth to her first baby "three weeks ago," she told friend Greta Gerwig at Stella McCartney's Paris Fashion Week show Sept. 30.

As seen in video footage captured by French publication Paris Match, Pauline broke the baby news to the Barbie director after posing for photos outside the runway show.

"I just had a baby," she gushed to Greta, prompting the filmmaker to reply with amazement, "No!"

Pauline has not publicly revealed the identity of her baby's father, though she was seen introducing him to Greta at the fashion event. 

"We just had a baby," the 32-year-old continued as she wrapped her arm around her partner. "Three weeks ago."

Pauline—the older sister of Timothée Chalamet—confirmed her pregnancy last Paris Fashion Week in June, proudly touting her baby bump alongside pregnant designer Jeanne Damas at a haute couture presentation.

At the time, the actress donned black bodycon dress with cap sleeves as she posed for a photo with Jeanne, who bared her bump in a figure-hugging pink frock.

Pauline was also spotted caressing her growing belly when she hit up the Patou fashion show that same week.

And while Pauline has kept much of her love life out of the public eye, she's been open about her strong bond with her 28-year-old brother. In fact, she doesn't even mind that Timothée is a fan of Sex Lives of College Girls—sex scenes and all.

"My brother loves it," Pauline, who plays Kimberly on the Max series, told E! News in 2022. "You'll have to get the story from him, because I believe he did watch it with one of my parents."

Likewise, Timothée considers Pauline to be his "best friend."

"I have an incredible relationship with her," he shared in 2020, jokingly noting that they—like many siblings—had a playful "grudge" against each other growing up. "All in all, it was healthy by the end."