Planet Fitness' "gym etiquette" policy is making headlines again after a pregnant woman says she was asked to leave a South Carolina establishment for exposing her belly.

Melissa Mantor, who is 18 weeks pregnant, claims she was working out on the treadmill at the Planet Fitness on Sam Rittenberg Boulevard in Charleston, S.C., when an employee approached her and asked her to leave because she was in violation of the dress code, ABC affiliate WCIV reports. Mantor was wearing a tank top with spaghetti straps at the time, but she said had worn the top before -- even while taking her membership photo -- without issue.

"I was very confused," Mantor told WCIV. "She continued telling [me] that my belly was hanging out and I need to get it covered up. I told her at that time, 'Of course my belly is hanging out, I am pregnant.' She handed me a very large T-shirt while telling me that what I was wearing was inappropriate and in violation of their dress code."

She refused to change into the complimentary T-shirt.

"I have to stick up for pregnant moms and for women, you know?" Mentor, who was embarrassed by the incident, added. "This is not okay. It's really not okay."

The Planet Fitness dress code prohibits jeans, string tank tops, boots and sandals so as to "promote a non-intimidating atmosphere." Club managers at nationwide locations are responsible for using their discretion to determine what is appropriate and inappropriate.

McCall Gosselin, the director of public relations at Planet Fitness, told The Huffington Post in an emailed statement that the particular Charleston location has a policy that prohibits bare midriffs.

"In this instance, staff informed the member of the policy and offered her a free T-shirt to complete her workout. She was not asked to leave the gym as a result of her attire," Gosselin said. "The franchise owner has contacted the member directly to address the misunderstanding. At Planet Fitness, we are committed to providing a comfortable and welcoming environment for everyone, and we are working with the franchise owner to clarify the dress code policy moving forward.”

Last month, Planet Fitness customer Tiffany Austin claimed she was approached by an employee at a Richmond, Calif., location and asked to put on a shirt because she was "too toned" and "intimidating" to other patrons. The company claimed Austin was in violation of the dress code.