The Californian mother, Melody, took a screenshot of an email she received from Huggies and posted it on Reddit.
She wrote: "Is it just me or did this Huggies ad photoshop a thigh gap on a toddler?"
"The picture looked manipulated. Really manipulated, like what you see in fashion magazines to make models too thin and too perfect," Melody told Yahoo Parenting.
"I just felt like there’s no need for airbrushing to exist on an ad about babies," she added.
"All babies are wonderful and super cute. A baby is perfect no matter what."
When she posted the photo on the social networking site, not everyone agreed it had been photoshopped.
Some believed it was the toddler standing in a funny angle.
Others believed it was the nappy that was photoshopped.
And some did agree that the photo looked like it had been photoshopped.
Huggies in America responded to requests and denied claims the baby had been photostopped.
A spokesperson told HuffPost UK Parents: "We can assure you that we did not alter the natural shape of the baby’s body in the creation of the ad referred to.
"We realise all babies are different and celebrate those differences in our photography and communications."