When child care centers were forced to close in the pandemic's early months, hundreds of thousands of American working mothers lost their jobs, new research shows.

The study is just the latest illustration of the toll the pandemic has taken on working women in the United States.

Over the first 10 months of the U.S. pandemic, more than 2.3 million women left the labor force, according to the National Women's Law Center. That compared with just under 1.8 million men.

That was, in part, because many job losses were in industries where women make up much of the workforce. On top of that, working mothers — more than fathers — faced the difficulty of having kids home from school or day care.

The new study looked specifically at the impact of pandemic child care closures.

It found that in states that had closures in spring 2020, women's job losses were particularly acute. In contrast, the employment decline among men was similar to that of men in other states.

Nationwide, the gap amounted to about 611,000 lost jobs among working mothers.

"The effect was concentrated among women with young children," said lead researcher Yevgeniy Feyman of the Boston University School of Public Health.

That, he said, suggests that child care closures, themselves, fueled many of the excess job losses.

That is likely the case, agreed Rasheed Malik, who studies child care policy at the Center for American Progress, a nonpartisan policy institute in Washington, D.C.

"Prior to the pandemic," he said, "there was already a strong relationship between local availability of child care and women's participation in the workforce."

The pandemic only worsened the longstanding problem of child care "deserts," Malik said. Those are areas across the country — typically low-income — where working parents lack affordable, quality child care options.

Child care centers did reopen in closure states by June 2020, according to Feyman's team. But while many women and men did go back to work, women still lagged behind as of December 2020, the study found. They were less likely than men to be employed, and their employment rate remained below its pre-pandemic level.

Simply allowing child care centers to reopen didn't necessarily solve families' problems.

For one, Malik said, an estimated 10% of programs closed for good. And at those that did survive, staff reductions meant fewer families could be served.

"Getting back into the system wasn't just a matter of going back to the program you'd been in," Malik said.

The findings are based on data from a monthly labor force survey. It included nearly 49,000 U.S. adults, including more than 13,000 from states where child care centers shut down by April 2020.

Employment among men and women in all states dropped sharply in April 2020, but women in states with child care closures saw the steepest drop-off. The likelihood of women being employed during the closure period was 2.6 percentage points lower, compared to men.

That translated to 611,000 job losses among 23.5 million working mothers, the researchers estimated.

To Feyman, one implication is that American workers need better paid family leave, and a "cultural shift" where not only women, but men, take it.

Malik pointed to some fundamental issues that make finding reliable child care so difficult, pandemic or not.

Unlike public education, he said, the child care system is "market-based" — with programs concentrated in more affluent areas where families can afford the cost.

"We think of it as a market failure," Malik said. "We don't have public school deserts, but we do have them in child care."

To make quality care accessible to more families there must be some level of government subsidy as well as assistance to low-income families, he said.

That "investment in families" would be repaid in parents' increased productivity and the educational and social benefits young children gain from being in high-quality programs, Malik said.

Another problem is the field's generally low pay and high turnover.

"These are difficult jobs," he added. "The work is rewarding, but definitely not financially rewarding."

Malik said that low pay is rooted in "historical bias" that undervalues the work of women, who make up the vast majority of the child care workforce.

"It's about time we honor the decades of hard work they've given us," Malik said.