The 2010 Patient Protection and Affordable Care Act requires that workplaces with more than 50 employees create a separate room that is not a bathroom for nursing mothers to pump, and also mandates that they receive two 30-minute breaks. But experts said that's not enough support for nursing mothers.
Not every breastfeeding woman works in a place with more than 50 employees, and the breaks are often unpaid, Noonan said.
And another problem with the law, said Philadelphia-area women's and civil rights attorney Jake Aryeh Marcus, is that no penalties are imposed on employers who don't comply unless a woman is fired.
"The women who have laws assisting them have state laws assisting them," she said.
There are 19 states with laws in place protecting breastfeeding women against discrimination at work. The law in another state, Montana, protects only public employees. Not all states have enforcement provisions in place, however.
"There has been some positive change," Marcus said. "There are some business that have voluntarily complied with the law without doing a more in-depth examination about whether they actually had to." Some of these businesses have done so, she said, to avoid having formal complaints lodged against them.
There is another proposed law -- the Breastfeeding Promotion Act -- that was introduced in both houses of Congress and is currently in the House Committee on Education and the Work Force. If eventually passed, this law, Marcus explained, would make breastfeeding discrimination akin to sex discrimination.
A study published in March found that many mothers felt pressured to breastfeed and felt guilty if they didn't.
"There are many competing demands on new parents: lack of sleep; crying, unsettled babies; other children to look after; and work commitments," lead author Dr. Pat Hoddinott at the University of Aberdeen in the United Kingdom told ABC News when her research was published. "Families very carefully weigh the long-term benefits of breastfeeding with the family's immediate well-being.
"It puts a lot of strain on new families," Hoddinott said. "Instead of stating the World Health Organization guidelines, we should be telling women to breastfeed as long as they can. There's accumulating evidence that breastfeeding for as long as possible has heath benefits for both mother and baby."
The Centers for Disease Control and Prevention recently found that only 13 percent of new mothers in the U.S. were breastfeeding exclusively at six months. Breastfeeding advocates consider six months to be the best option for infants' health, and said they'd been pushing for mothers to receive more support.
"When mothers can't' breastfeed, it is almost always because the supports were not in place for her to do it, and those supports come from society and the health care profession," Dr. Kathleen Marinelli, a pediatrician at Connecticut Children's Medical Center in Hartford, told ABC News in March.
Given her own difficulties in breastfeeding on the job, K.M. now understands firsthand why many mothers stop nursing.
"Employers need to realize that there are benefits for them as well as for mothers and babies," she said. "My baby will be healthier, and I will feel better and less stressed, and will ultimately need less time off."
ABC News' Karin Halperin contributed to this story.