Ciara is definitely back in shape four months after giving birth to her first child.

On Friday, Oct. 3, the 28-year-old singer posted some steamy hot photos of herself on Instagram donning nothing but her Calvin Klein undies and bras.

In one photo, the "Get Up" hitmaker wore a sexy black sports bra and Calvin Klein underwear while seductively relaxing on bed. "I feel so proud to say that 4 months after delivering a 9 lbs. 10 oz. baby, I can finally rock My Calvin's! #mycalvins," she captioned the snap.

In another steamy photo, the Austin, Texas-born recording artist donned a matching grey Calvin Klein bra and undies. "After Delivering My Son I Feel Like There's Nothing I Can't Do. I Feel Like I Can Conquer The World. #ANewMe #NewMusic. So Proud To Rock #mycalvins 60lbs later!!" she wrote on the image-sharing site, along with the photograph showcasing her flat stomach.

During a January appearance on "The View," Ciara announced that she and rapper Future were expecting their first child together, Rap-Up reported.

And on May 19, Ciara gave birth to a baby boy, named Future Zahir Wilburn.

Ciara recently opened up to Us Weekly about how she managed to shed her baby weight in just a short span of time.

"You go from the mommy gym at home to the real gym and then you go to the stage. For me it's all about not only getting back into the place that I was in before. I had a baby but now, going even further," she told the celebrity and entertainment magazine on Aug. 8. "I want to be one of those moms and women that when I look back, I know that I always stayed focused. And I think it's about keeping your eyes on the prize."

Ciara has been working out daily with personal trainer Gunnar Peterson.

"When you say she's working out every day, that sounds like it's crazy but it's not," Peterson told People last month. "It's a ritual. She's showering every day too. She's not destroying herself."

The celebrity fitness guru continued: "She's working hard, she's getting it done, she's eating properly, she's getting sleep while she can, and so she's getting leaner and stronger. That's the way to be the best mom."

Peterson said that varying workouts is the most important factor in toning up Ciara's post-pregnancy body.

"The typical workout is that it's not typical," explained Peterson. "Depending on where we are in the week, there's a focus on pushing movements, pulling movements; there's lower body, there's working different planes of motion, whether it's front to back, side to side rotation."

"It's about keeping her moving," he added. "There are a lot of intervals in there. It doesn't make for a happy camper, but [it produces] great results. You see the body, she's already right there."