Women disproportionately don't get paid time off to pay for taking care of their kids ... or in geneal(The Image Bank/Getty Images)

Women already face many inequities in the American workplace. They receive less pay, and they take a financial hit when they have a baby, while men get a boost. And now, it appears, women are less likely to get paid time off, even though they typically need it more often.

You can draw that conclusion, at least, from a new report by the Families and Work Institute and the Society for Human Resource Management that found great disparities in the type of workers who receive paid time off -- either vacation time or sick days or more general paid leave. Nearly all-full time workers do. But less than a third of part-time workers do.

And there's the rub. Women are far more likely than men to work part-time. And the overwhelming reason is that they either choose to, or have no choice. Women, after all, are still doing about twice the housework and child care as their male partners.

It turns out that even after they make that sacrifice, they still get penalized in the workplace. By not getting paid leave, they risk losing income if they need time to take care of a sick kid or an aging parent.

The survey of 1,000 firms by the Families and Work Institute and the Society for Human Resource Management found that between 92 and 100 percent offered paid leave  to full-time workers. Typically, they receive 5 days of paid sick days, 10 days of paid vacation days or 15 days of generic Paid Time Off.

But the same was not true for part-time workers: Barely one-third offered part-time workers paid vacation days. About one in four offered paid sick days.

And while slightly more than half of the large companies with 1,000 or more employees offered part-time workers some kind of paid time off, the report found only 15 percent of small companies offered paid time off to part-time hourly workers and 18 percent offered it to salaried part-time workers.

The report authors warn that the lack of paid time off hurts the growing number of workers who cobble together multiple part-time jobs to make ends meet. “However they play it, they’re losing out on income if they take time off,” said Ken Matos, of the Families and Work Institute.

Though still a small number of workers, around 2 million Matos said, the share of workers stringing together multiple part-time jobs has risen 11 percent since 2007.

But those numbers pale in comparison to the number of women working part-time. Nearly twice as many women as men work part time, according to the Bureau of Labor Statistics - 9.8 million men in 2014 to 17. 7 million women. And the vast majority of women, about 13 million, work part time for “non economic reasons,” – which typically means juggling child care, elder care and other home front duties.

Part-time work in the United States tends to be of lower quality, anyway, compared to full-time work. A Bureau of Labor Statistics analysis in 2009 concluded that, in all but 12 of 194 different occupations, full-time workers earned more per hour by a statistically significant margin than their part-time counterparts doing the same job, but working fewer hours.

Other countries, including Germany, Britain and the Netherlands, give full-time workers the right to request part-time work without changing jobs or occupations, the economist Nancy Folbre has written. Part time work doesn’t necessarily sidetrack a career. And in The Netherlands, mothers as well as about one in three fathers work part-time schedules – the four-day a week schedule for men has come to be called the “Daddy Day” – and they all retain benefits and paid time off.

But things are different for part-time workers in the United States, where the ready supply of married and single mothers who need flexible schedules to accommodate their caregiving loads, Folbre wrote, “has made it easy for employers to designate such jobs as low-pay, no-benefit positions.”

Like getting no paid time off. For any reason.