Older millennial women who have delayed starting a family until they are more established in their careers may be reacting to this effect.
A recent Pew Research Center report found that 49 percent of Generation X women were mothers when they were ages 18 to 33 versus only 42 percent of millennial women in that range.
Though companies increasingly are expanding benefits to help workers have children, some employees may be reluctant to take advantage of these options, fearing resentment or losing their place on the career track.
In fact, more mothers with children under 18 are now in the workplace — 60 percent vs. 47 percent in 1975.
Kerr told CNBC that women who are further along in their careers are in a better position to negotiate their benefits when it comes to family leave.
Women who earn $75,000 or more take double the amount of maternity leave than women who make under $30,000, according to the Pew Research report.
"It's different if you're a highly valued employee than if you're on the bubble," Stewart Friedman, a Wharton School management professor, told CNBC. "It really matters what your position in the internal organization is and how much value you have."
Kerr added: "There are pros and cons to delaying pregnancy — I think the research is pretty good at showing that, in terms of your career, that waiting is beneficial in the long run."