Sales consultant Holly Waters says she was a top performer for the drug maker Novartis. But when she was about go on maternity leave, she was fired.

"I was seven-and-a-half months pregnant. There was no way I was going to be able to go out and find a job at this point," she told me for my ABC special "You Can't Even Talk About It."

Waters knew the law is on her side. The Pregnancy Discrimination Act makes it illegal to fire, or not hire, a woman because she is pregnant. The law even restricts workplace speech. Employers are warned that in a job interview they must never ask questions like, "Might you start a family?"

If Congress thought the law would end claims of workplace discrimination, it was wrong, as usual. Companies are increasingly being sued. Even a maternity-clothing chain was sued.

Waters's lawyer, David Sanford, filed a class-action lawsuit against Novartis. "If you get pregnant, you're in trouble at Novartis," he told me.

Novartis denies wrongdoing and points out that Working Mother magazine named it one of America's 100 best companies for women.

Sanford claims that his $200-million lawsuit will teach Novartis and other companies not to discriminate.

But Carrie Lukas says such lawsuits do more harm than good. Lukas is also a working mom, vice president of the Independent Women's Forum.

"If my employer decides they no longer want me as an employee, then it should be their right to fire me." she told me. "I understand the desire for people to have government step in and try to protect women, but there's real costs to government intervention."

These costs are rarely talked about publicly. But once Congress creates protected groups, some employers avoid hiring members of those groups. After the Americans with Disabilities Act became law, it was assumed more disabled people would enter the workplace. But a study by economists at MIT found employment actually "dropped sharply."

Likewise, "pregnancy protection" creates problems for women.

"Sometimes laws that are intended to help women like me actually end up hurting women like me," Lukas said. "All of a sudden, a potential employer is looking at me and thinking, 'She just might turn around and sue us.' That makes it less likely that I'm going to get hired. You raise the cost of hiring a woman like me."

And while some pregnant women work harder than any man, she says, let's be honest: Most pregnant workers impose costs on employers.

"Responsibilities are shifted each time I go to a doctor's appointment," Lukas said. "That means I'm unavailable to do whatever work needs to be done during that time, which means one of my colleagues is often picking up the slack."

As free-market economists have long suggested, there's a way to resolve such a conflict: voluntary exchange for mutual benefit. Carrie and her employer made a deal that works for both of them. She works fewer hours and earns less money.

I confronted Sanford with the idea that lawsuits he files actually harm women because companies view them as potential lawsuit bombs.

He was unfazed: "If they do take that position, they'd be violating the law. If companies lose money because of it -- and they may -- that's not necessarily a bad thing from a societal perspective."

I think it's a very bad thing. Employment and productivity matter. But viewers agreed with him. I got hate mail:

"It is unbelievable that ABC would consider airing this piece! ... This turns back the clock 30 years, and Betty Friedan is rolling in her grave!"

"What in the heck is wrong with you, John Stossel? This kind of backwards thinking only exists in third world countries."

"Fire Stossel."

How would the job market work without discrimination laws?

"You don't have to hire me, and I don't have to work for you," answers Carrie Lukas.

Who would hire pregnant women?

"Plenty of employers. ... Women are incredibly productive members of the workforce," Lukas said. "We have a lot to offer. If an employer is going to discriminate against enough people, it's going to be bad for them in the long run. It's a bad business practice. And that's the best way to prevent discrimination."