Flu season is upon us. From November to March, an estimated five to 20 percent of U.S. residents—or 16 to 63 million Americans—will get the flu. One study estimates that the flu leads to $16.3 billion in lost earnings each year.

American workers who have children not only have to worry about missing work when they are ill, but also when their kids get sick. A sick child can often mean having to call into work to take a day off, which matters a lot to the 59 percent of married couples with children in the U.S. who report both parents working.

A new study looks at the gender and financial breakdown of how families with working parents cope when kids get sick. The study finds that women are 10 times more likely than men to take time off to stay home with their sick children. Mothers are also five times more likely to take their sick kids to doctors appointments.

For working moms, 39 percent report missing work to care for their sick children, 33 percent report sharing the responsibility with their spouse, 16 percent report calling someone else to help, and 6 percent report their partner taking time off. Of the 39 percent of women who report taking time off to care for their sick children 60 percent report not getting paid. That’s up significantly from 2004, when 45 percent reported not being paid for missing work.

That’s a lot of unpaid work considering that there are 72 million women in the U.S. work force today (which is about 47 percent of all workers in America). Labor force participation is 76 percent for mothers with children aged 6-17, and 64.7 percent for mothers with children age 6 and under. The Labor Department reported that labor force participation for new mothers is higher than ever.

With an estimated 40 million workers in the U.S. not getting paid leave, and women still trailing behind men in earnings, why are women more likely to take unpaid leave to care for their sick kids? A Pew analysis of the American Time Use Survey reports that for dual-income couples, mothers report spending nearly twice as many hours each week on child care than fathers. Sheryl Sandberg suspects it might be plain old guilt that prevents them from working. And even for working moms who have a paid-leave policy, facing coworkers after taking time off to care for sick kids can be anxiety inducing.