Meghan Trainor Shows Off Baby Bump in Adorable Video — with Cameos from Son Riley and Chris Olsen

https://www.instagram.com/p/CodqDBPoPdJ/ meghantrainor Verified Never did this one when I was pregnant with Riley. HOW AM I ALREADY ALMOST HALF WAY THERE��? #18weekspregnant #secondtrimester 2h
https://www.instagram.com/p/CodqDBPoPdJ/ meghantrainor Verified Never did this one when I was pregnant with Riley. HOW AM I ALREADY ALMOST HALF WAY THERE��? #18weekspregnant #secondtrimester 2h

Meghan Trainor/Instagram

Meghan Trainor's getting closer to the finish line with her second pregnancy, but she's still got the moves!

Grooving to Starrkeisha's "The Baby Momma Dance" in an Instagram-posted video on Thursday, Trainor executed the accompanying dance to the viral hit in perfect slinky fashion.

Despite being clad casually in an oversized sweatshirt, she still managed to show off her growing bump while proving her hashtag #18weekspregnant ain't nothing but a number.

The impromptu performance came complete with an appearance from 25-year-old TikTok star and close friend Chris Olsen, who squats down to perform a lip-sync of the chorus.

Meanwhile, Trainor's firstborn, 2-year-old son Riley, makes a cameo in the video as well, but appears completely unimpressed, sucking on what appears to be an applesauce pouch and fiddling with a toy while giving a bored glance to the camera.

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"Never did this one when I was pregnant with Riley," Trainor captioned her post, adding, "HOW AM I ALREADY ALMOST HALF WAY THERE?"

In terms of being prepared for her expanding family, the "All About That Bass" singer, 29, said that she and her Spy Kids actor husband Daryl Sabara, 30, are preparing their home for their new arrival.

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"Everything's done," Trainor told PEOPLE this week. "We know the gender. We know the name. We know the full name."

"I've already painted the room. I'm prepared this time," Trainor shared.

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In addition to getting ready for her second baby, Trainor is also preparing for the release of her first book, Dear Future Mama, in which she opens up about her experience with pregnancy, with weigh-in from her OB-GYN, registered dietician and personal trainer.

She added that she hoped the book will be beneficial to first-time mothers.

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"I know not everyone has access to the amazing people who I have access to. So my dietician is in the book and gives advice for every trimester. My trainer is in the book, and there's pictures showing you what you can do for workouts because you can still work out when you're pregnant, and it's safe — I didn't know that."