Melissa Mantor, 31, was asked to leave by a female employee of Planet Fitness in South Carolina, because her pregnant 'belly was hanging out.'
The tank top and leggings - which she wears in her membership photo - was deemed not in keeping with the fitness centre's dress code, despite Melissa having worn it dozens of times before to work out.
'I went to the gym for my usual workout but it was the first day that I was visibly pregnant,' said Melissa.
'I was on the treadmill, when a female employee came up to me and said "I'm going to have to ask you to leave, you are in violation of the dress code."'
The employee continued: '"Your belly's hanging out and I need to get it covered up." I told her: "Of course my belly is hanging out, I am pregnant."'
Mrs Mantor has now cancelled her membership with the gym.
'I can't go to a gym where they would make someone feel bad about themselves when they are trying to stay in shape,' she said.
In a statement from the director of PR for Planet Fitness, the company denied that Mrs Mantor was asked to leave the premises, and claimed she was offered a free t-shirt to complete her workout in.