You've heard of the gender pay gap - now we're learning about the mom pay gap.
A new study found moms with one child make 15% less than women who don't have kids. Mothers with two kids make 13% less, while moms with three or more kids make 20% less.
A professor at the University of Massachusetts who helped with the research says there's no reason for mom's to indicate they are moms.
Other research has shown that men make more money as they have kids.