Nicole Richie celebrates 18th birthday of daughter Harlow, now 'Kate'

Nicole Richie has marked her daughter's 18th birthday.

In a celebratory post to Instagram, she also revealed that her teenager may not go by the name Harlow anymore.

On Monday, the actor shared a carousel of photos depicting herself and her daughter, Harlow Winter Kate, posing together throughout the teenager's life, from newborn to now.

"18 years of you @katemaddennn," Richie wrote in her caption. Her husband, Joel Madden, commented on the post, writing, "That's my girl."

Fans were quick to point out that the account Richie tagged was under the name Kate, one of Harlow's middle names and speculated that the teenager may go by that name instead of Harlow.

"Happy birthday!? Did she change her name?" one follower commented.

Richie shares her daughter and her son, Sparrow, 16, with Madden.

She and the Good Charlotte singer met in late 2006, and welcomed daughter Harlow in 2008 and son Sparrow in 2009. They became engaged in 2010, and married in December 2010.

In October, Richie spoke with People about her two children. Asked if there's been anything that surprised her about having teenagers, Richie said it's been nice to see them transition.

"I'm seeing my kids at an age where I remember everything from that age, so they'll be telling me stories of whatever the comings and goings of them and their friends, and it sounds exactly like what I was going through senior year," she shared.

"It's fun. It's like a TV show."