Britney Spears says she has 'small belly' after pregnancy announcement: 'At least my pants fit'

 Britney Spears is happily documenting her pregnancy following this week's announcement she's expecting her third child.

The pop star posted a video shared to Instagram on Tuesday in which she calls attention to some of the bodily changes she's experiencing.

"So I have to model my clothes now before I really start showing…," her Instagram caption begins. 

In the beginning of the one-minute clip, Spears rocks her hips from side to side as she wears a floral crop top accessorized with a flower choker, and low-rise gray pants, exposing her midriff.

"I had to do the flower n my neck like @sarahjessicaparker … I actually do have a small belly here but at least my pants fit … Well barely!!!" Spears' caption continues.

The video continues to show the "Toxic" singer in a variety of other outfits. One seemed to be an ode to her "Baby One More Time" music video as she wore a white buttoned-down shirt tied above her belly with a black pencil skirt and heels. Another look shows the starlet in a floral black and red mini dress with black combat boots.

"Psss is anyone curious why I’m 4 sizes smaller by the door ???" her caption concludes.

The 40-year-old pop star took to Instagram on Monday, sharing an image of a pink teacup and flowers with a lengthy caption.

"I lost so much weight to go on my Maui trip only to gain it back," she began. "I thought ‘Geez … what happened to my stomach ???’ My husband said ‘No you’re food pregnant silly,'" referring to Sam Asghari, 28.

"So I got a pregnancy test … and uhhhhh well … I am having a baby."

The star went on to say, "I obviously won’t be going out as much due to the paps getting their money shot of me like they unfortunately already have … it’s hard because when I was pregnant I had perinatal depression … I have to say it is absolutely horrible."

"Women didn’t talk about it back then … some people considered it dangerous if a woman complained like that with a baby inside her … but now women talk about it everyday … thank Jesus we don’t have to keep that pain a reserved proper secret."

Spears concluded with, "This time I will be doing yoga every day !!! Spreading lots of joy and love."

A rep for Spears didn’t immediately respond to Fox News’ request for comment. 

Her fiancé, Asghari, took to Instagram on Monday to confirm the news, sharing a picture of a family of lions with a caption detailing what fatherhood means to him. 

"Marriage and kids are a natural part of a strong relationship filled with love and respect. Fatherhood is something i have always looked forward to and i don’t take lightly. It is the most important job i will ever do," he wrote, adding a praying hands emoji.

Meanwhile, some of Spears' fans were confused by her "food pregnant" comment. 

Spears shares her two sons, Sean, 16, and Jayden, 15, with her ex-husband, Kevin Federline. 

Federline’s attorney, Mark Vincent Kaplan, told NBC News on Monday, "He wishes her the best for a happy, healthy pregnancy and congratulates her and Sam Asghari as they plan for the excitement of parenthood together."