A pregnant Sydney mum walked into a gym class. The instructor's response left her shaken.

For many, the thought of being singled out by a gym instructor is a legitimate fear when they enter a packed-out fitness class.

But being singled out and forced to leave? Well, that’s enough to make you never want to go to the gym again.

For Natalie Hillar, a pregnant mum-of-two and gym enthusiast from Sydney, being told to leave a Fitness First Body Combat class last week left her no less than stunned.

On entering the class and finding herself a spot near the back, as she has on many occasions throughout her current pregnancy and two pregnancies prior, Natalie prepared herself for the class while the instructor gave the usual disclaimer.

Then, much to Natalie’s surprise, the instructor addressed her directly.

“She started the class, then she stopped and said: I don’t know if everyone heard me at the beginning, but I won’t teach this class to pregnant people,” Ms Hillar, who is six months pregnant, recalled of the incident last Wednesday.

“I didn’t think I’d heard her correctly when she first said it…I just thought ‘that doesn’t sound right’ and I was a bit confused.

“About 20 seconds later, she glared at me right at the back and said ‘I can see I still have pregnant people in this class and I refuse to teach this class to pregnant people’,” the 40-year-old communications company director said.

Promptly picking up her drink bottle and towel, Natalie headed for the door as the instructor called out: “I know you’re upset, but it’s for your own good love.”

“I was honestly glaring at her, I wanted to do a whole lot more but you don’t, you know,” Natalie said.

Feeling shocked by the incident, she complained to reception.

“They said “she can’t do that” one girl said “that’s discrimination”.

“Everyone was really good about it, but I just felt so frustrated. I just wanted to be in the class, I don’t think I was treated right.”

A gym patron of many years, Natalie feels passionately that she knows her body and her limits well enough to decide what is the right amount of physical exertion while pregnant.

She felt this was an instance of an outsider forcing their opinions and beliefs upon her about what is "safe" during pregnancy.

"Everybody's different. I had a message from a lady who said she ran five miles the morning her daughter was born, and taught body pump up until the week she gave birth. For me - that's too much, but everybody's different, it's up to you."

"I did Les Mills workouts right up until I gave birth to my last child...my doctors have always said it's fine, and I don't do the class with as much intensity as I normally would."

"(The instructor) took it upon herself to enforce what she thought...I'm surprised Fitness First allow people to express such strong opinions like that."

But while Natalie was initially angered by the experience, she says all she wants as a result is "further education" for instructors on the benefits of exercise during pregnancy.

"At first I was angry, and stunned. But I was just thinking "she needs some education". Clearly she doesn't realise it's actually healthy to exercise when pregnant," said Natalie.

After lengthy communication with Fitness First, who she says have been cooperative throughout the complaints procedure, she may have succeeded in improving the gym experience for pregnant women going forward.

A Fitness First spokesperson told Mamamia:

“At Fitness First, the safety of our members is our number one priority. We understand the level of exercise during pregnancy is personal and usually determined by pre-pregnancy fitness levels and advice from general practitioners. In addition to advice from their GP, we recommend any pregnant members notify the group fitness instructor prior to participating in a class.

"All of our group exercise instructors are required to make members aware of any risks and recommend against exercises should they be unsafe. In this case, this was the professional recommendation given."

But after our initial contact with the gym, we have since been informed that an apology has been issued.

"I received a verbal apology from Fitness First, they are reviewing their policies and procedures based on my experience and feedback," Natalie said.

She added that she has attended the gym since the incident and "will always approach the instructor before a class" in the future.

"I wasn't aware that's what I had to do, and I've been going to the gym for many years, but from now on I'll continue to have a chat with the instructor before the class so this doesn't happen again."