Lena Dunham Auctions the Sweater Off Her Back for Planned Parenthood -- See the Bra Selfie!

This video is unavailable because we were unable to load a message from our sponsors.

If you are using ad-blocking software, please disable it and reload the page.

Anyone who has seen Girls knows that Lena Dunham has no problem baring her body. Thursday night was no different when she stripped down for a good cause.

Dunham showed up to a Planned Parenthood event wearing an eye-catching sweater that she first brought attention to via Instagram.

WATCH: Lena Dunham Actually Grants Mindy Kaling's Awesome Birthday Wish

"Rollin to the @plannedparenthood Los Angeles Champion of Choice event and there was only one sweater that would do @rachelantonoff," she captioned the pic.

The burgundy sweater had a pink ovary shape on it, and was designed by Rachel Antonoff, the sister of Dunham's boyfriend Jack.

Dunham didn't wear the sweater home that night but instead took it right off her back and handed it to the highest bidder. "The @plannedparenthood event in LA tonight was so crazy inspiring," she captioned a selfie of her bra. "I also spontaneously auctioned the ovary patterned sweater off my body for a nice 4k to benefit PP... Had to walk home in my skivvies and a men's coat #worthit #onbrand #standwithPP."

While she didn't take her shirt off  during her visit to The Ellen DeGeneres Show, she did get pretty candid as to why she and Antonoff have yet to get engaged.

Dunham and her musician beau had said that they would wed once gay marriage was legal in the United States, but have since backtracked a bit on that comment.

MORE: Lena Dunham Calls Out Justin Bieber's 'What Do You Mean?' Lyrics

"We were celebrating, and then suddenly the texts just started coming from our friends, from our mothers, from our exercise instructors being like, 'Finally, it’s your time.' And we kind of looked at each other and were like, 'Oh God, what have we done?'" she recalled, admitting they were "hiding behind fake liberal ideals."

She did reveal that she still plans on saying "I do" to Antonoff -- just not right now.

WATCH: Lena Dunham Gets a Running Coach -- I Used to 'Run Like a Wounded Baby Pterodactyl'

"We’re not gonna suddenly just get engaged because it became legal," she said. "We better wait for a moment where we feel excited about this. I’m excited to marry him at some point, but it felt like a lot of pressure to just go for it that day.

Dunham quipped, "I did start to ask are there a lot of heterosexuals using this as an excuse to avoid commitment."

Check out more of the Girls star's interview on Ellen

Related Gallery