Image credit: Courtesy Kristi Rifkin

Kristi Rifkin had been working at T-Mobile Call Center in Nashville for four years when she got pregnant with her third child. She says she loved her job.

"I had a great run," Rifkin, 40, told ABC News. "I was making bonus. T-Mobile was good to me. I never had a problem getting a schedule I wanted. I enjoyed it. I had even left another company to work at T-Mobile because they had great benefits."

But her good will toward the company changed once she got pregnant.

According to Rifkin, the pregnancy-her second (she has one stepson)-was a difficult one, and she was going to the doctor twice a week, seeing both a regular obstetrician and a high-risk obstetrician. She was also required to drink "tons and tons" of water - which, in turn, resulted in frequent trips to the bathroom. This did not sit well with T-Mobile, she said.

"They give you two 15 minute breaks and a 30 minute lunch," said Rifkin. "If you can't take care of your biological needs in that time period, you don't go."

Before her pregnancy, this wasn't an issue. But as she explained in a blog post on MomsRising.org, frequent jaunts to the bathroom would cut into what was known in the call center world as "adherence" - a metric that measures the degree to which employees meet their quota for being on the phone.

"You have different numbers you have to meet each month, and if you don't meet them they can fire you," she said. "The thinking is that if you're off the phone and you're not doing what you're supposed to be doing, then there are customers waiting to talk to you."

She tried to hold off on eating and drinking; she needed the health insurance the job provided. But the baby was suffering, Rifkin said, and she had to start drinking water again.

Finally, she said, her supervisor pulled her aside and told her to get a note from her doctor explaining that she needed to go the bathroom often. "At that point, I thought my head was going to launch off my shoulders," said Rifkin. "'Are you serious? I need to get a note from my doctor to go to the toilet?' This is a basic biological need.'"

But Rifkin did as she was told; she got the doctor's note and cleared it with Human Resources. She was told that she could use the rest room any time she needed to, she said, but that she would have to clock out. When she returned from that bathroom, she would have to clock back in. "This meant I was out of work for five minutes," she said. She had to write the hours down and turn it into her supervisor, just to make sure she wasn't taking advantage of the situation.

"I ended up using my vacation time to use the bathroom," she said.

But she still wasn't eating and drinking as she was supposed to. Her blood pressure skyrocketed. She was stressed and anxious.

She finally went on the Family Medical Leave Act, which requires employers to provide up to 12 weeks of unpaid, job-protected leave to eligible employees, seven weeks before her son, Ian, was born, on May 14, 2010. A month and a half after she returned to work she was fired, she said.

The reason? Rifkin says she was summarily fired after she failed to remove an extra-charge feature from a customer's account, the commission for which was 12 cents. She says the rare error occurred when she either forgot to remove the charge or removed another charge instead.

She got no severance, she said, and now pays for medical expenses out of pocket.

Rifkin said she has no plans to sue the company; it's too expensive, and Tennessee is an at-will employment state. "They can fire you for any reason," she said

The US. Department of Labor reports that only eight states require paid rest periods and Tennessee is not among them.

"There is no specific legal requirement that requires employers to let their employees use the restroom," Paula Brantner, the executive director of Workplace Fairness, which provides legal information about workers rights. However, "If a pregnant woman is the only employee being forced to clock out, and they don't require males or non-pregnant females to do so, it would seem to me that would be pregnancy discrimination."

In an email statement to ABC News, T-Mobile spokesperson Glenn A. Zaccara said that he could not comment on a specific individual. But "T-Mobile employees enjoy generous benefits including paid-time-off and short and long-term disability coverage," he said. "The company has leave of absence policies in line with regulatory requirements."

Rifkin was not impressed. "I'm done with T-Mobile," she said. "I don't want anything to do with them anymore."