When Garrett was 3 months old, she went back to work and was surprised by her employer's reaction.
"My very first day back I was told to put my (baby) pictures away," she told CBS News Correspondent Jane Clayson.
Walsh's successful career as sales rep for National Computer Systems suddenly changed.
"I almost felt as though I'd committed a crime in having a child," she said.
Her supervisor constantly reminded everyone Walsh was a new mother. After she fainted at work one day -- and ended up in the hospital -- her boss came to her cubicle and said, "You better not be pregnant again."
Walsh quit her job after 16 months. She sued NCS in federal court for discrimination and won more than $600,000. NCS is appealing the verdict and denies it discriminated against her, saying she "misinterpreted" or "misunderstood" her supervisor.
Firing or demoting a pregnant woman at any company with more than 15 employees has been illegal since 1978. But this kind of discrimination can be subtle and hard to prove, creating a new barrier for women in the workplace.
"Most women never get near the glass ceiling. They're stopped long before by this maternal wall. What these cases show is that women, to their credit, have begun to challenge that maternal wall," said Joan Williams.
In a new study, the American University law professor found dozens of women winning maternity discrimination cases across the country -- most in just the last ten years.
Asked if the situation for pregnant women was getting worse, Williams replied, "I don't think it's getting worse. I think mothers are getting more savvy."
Employment lawyers say state and federal laws make companies more vulnerable to court losses.
Employment lawyer Susan Fentin agrees. "It's a very, very low bar. The courts have set it up as a low threshold specifically to encourage people to be able to claim their rights. It's pretty easy to claim discrimination."
Shireen Walsh wasn't going to sue her former employer until she realized she was afraid to get pregnant again. Today, more than five years later, she has both a new job and another baby on the way.
This time her boss' reaction was more positive.
"My boss, when I told him I was expecting -- 'Hip, hip hooray! Oh, this is great!' ... It was just a far different reaction," she said.
And a reaction more in line with laws that guarantee motherhood can't come into play when the issue is a woman's work.