Colton Haynes poses with 'baby bump'

Actor Colton Haynes celebrated an Instagram milestone by sharing a photo of himself cradling his "baby bump".

The Arrow star reached an impressive four million followers on the photo sharing site on Thursday (31Mar16), and to thank all his fans, he posted a shot taken by his photographer friend Tyler Shields. The snap features the actor standing without a shirt on and looking pensive as he protrudes his stomach to make it look like he's holding a growing baby bump.

"So happy to make more art with @thetylershields," Colton wrote. "Today I hit 4 Million followers on Instagram. I want to take a moment to express my gratitude & love to all of you who’ve continued to support me.

"I know I can be odd & come off a bit weird sometimes but honestly... my career & life didn’t actually start flourishing until the day I decided to listen to my own instincts and do what I want to do/be myself and not mask that. I'm not going to conform to what people think is normal... and neither should any of you. That’s so freakin boring haha (sic)."

He continued, "Be weird. Be yourself cause at the end of the day... hat’s honestly all that matters. Let people see the real, imperfect, flawed, quirky, weird, beautiful, & magical person that you are. Sending love to all of you (sic)."

He later retweeted a link to the photo and joked, "It's a boy."

Colton has been hitting headlines over the past few months with his candid demeanour online - in December (15), he opened up about his battle with anxiety, and in January (16), he appeared to confirm reports that he's gay.