Child care costs are surging. According to a new study from LendingTree, sending two kids to child care is about 40% more expensive than the cost of rent in 100 of the nation’s largest metropolitan areas.

In many cities, the child care-to-rent ratio is very unbalanced. According to that study, the average monthly cost of full-time child care for two kids is 39.4% higher than the average rent for a two-bedroom unit.

It’s a problem affecting both large and small cities in America. “This is not just a large city problem; this is something that’s going on in smaller cities as well,” said Stan Oklobdzija, a professor in the School of Liberal Arts at Tulane University.

The study found that in some cities, families can expect to pay more than double the average rent for child care. Springfield, Massachusetts, had the highest child care-to-rent ratio, with families paying 136% more per month. Syracuse and Buffalo, both in New York, rounded out the top three.

“Some of our states that are lowering the cost of living, you know, it’s less, but it’s still $800-$900 per month for a child, and that’s a lot of money,” said Cynthia Osborne, a professor of early childhood education at Vanderbilt University.

When it comes to paying the most for child care, the study found Washington, D.C., had the highest average cost, followed by Boston, Worcester and Springfield, all in Massachusetts.