In the Season 4 clip, Kourtney was sitting next to her sister, Kim Kardashian, during a confessional.

Kourtney was wearing a black bra with a leather jacket and her cleavage on full display.

She had her black locks pulled back tightly into a bun.

The reality star accessorized with a thick, lace choker that covered most of her neck.

An Instagram user (@kardashianclips) posted a clip of the episode on social media and questioned why Kourtney’s boobs appeared to be moving on their own.

“What’s happening lol,” the user captioned the post, which included a video clip of the episode.

The post has received more than 34,000 likes and plenty of comments.

Several people said Kourtney simply took a breath, which caused the movement, while others suggested that plastic surgery was to blame.

One person wrote: “This is because she has under the muscle implants. I had them and they’re very uncomfortable. I couldn’t take it anymore, so I took them off. It was traumatic!”

A second said: “Those implants are stronger and would last longer than Kim’s marriages lol.”

A third wrote: “Muscle flex under implants.”

“The baby was probably moving,” another person commented.

“She’s pumping milk,” said another person.

Kourtney was pregnant with her fourth child, Rocky Thirteen, during the taping.

The reality star also shares three kids with her ex Scott Disick: Mason, 13, Penelope, 11, and Reign, 8.

Kourtney gave birth to baby Rocky – her first child with her Blink-182 rocker husband, Travis Barker, 47, in early November.

Travis also shares two children, Landon and Alabama, with his ex Shana Moakler.

Kourtney has led a fairly quiet lifestyle after she endured a scary pregnancy and gave birth to Rocky.

In September, the reality star underwent a surgical procedure to save the life of her unborn child at the tail end of her pregnancy.

On September 1, Blink-182 announced that they’d canceled their UK and Ireland tour dates for Travis to attend to an urgent family matter, although the band didn’t specify what the emergency was.

A day later, Kourtney and Travis were photographed exiting a Los Angeles hospital with serious looks on their faces.

The Poosh founder addressed the scary episode on September 6 on Instagram, writing: “I will be forever grateful to my incredible doctors for saving our baby’s life.

“I am eternally grateful to my husband who rushed to my side from tour to be with me in the hospital and take care of me afterwards, my rock.”

She also said: “Praise be to God. Walking out of the hospital with my baby boy in my tummy and safe was the truest blessing.”

6Kourtney (right) and her husband, Blink-182 rocker Travis Barker, welcomed Rocky in early NovemberCredit: Instagram / kulikulikulik6Travis (left) also, shares two children, Alabama (second from left) and Landon (second from right) with his ex Shanna MoaklerCredit: instagram/@kourtneykardash6Kourtney shares three other children with her ex Scott Disick (second from right): Mason (right), Penelope (left) and Reign (second from left)