Having a baby today costs a lot more than it did in 2008. It's not that doctors are charging more — the out-of-pocket expenses have gone up by as much as 72 percent in some cases.

The Affordable Care Act (ACA) requires large, employer-sponsored health plans to cap out-of-pocket costs for maternity care. But the ACA allows these plans to impose cost-sharing measures, such as co-pays and deductibles, before their coverage kicks in.

Out-of-pocket expenses for maternity care increased from $3,069 in 2008 to $4,569 in 2015.

Researchers at the University of Michigan looked at the cost of maternity care, and the costs that were covered by employer-sponsored plans versus those costs patients paid out-of-pocket before and after the implementation of the ACA. What they found is that women were paying more, lots more.

Since the ACA was implemented, women are responsible for more of the costs of maternity care. “We were surprised to learn the vast majority of women paid for critical health services tied to having a baby,” author, Michelle Moniz, said in a statement. Given the greater burden of out-of-pocket costs, many mothers-to-be decide not to opt for important tests and checkups. “These financial burdens put women at risk for delaying or missing maternity care, which we know can lead to poor outcomes for mothers and babies,” said Moniz.

A nationwide sample of over 650,000 women enrolled in nearly 84,000 different employer-sponsored health plans was used for the study. The data set covered more than 804,000 deliveries between 2008 and 2015.

Out-of-pocket expenses for maternity care increased from $3,069 in 2008 to $4,569 in 2015, for both cesarean sections and vaginal deliveries. This cost increase is largely due to a spike in deductible payments during the study period. The average deductible payment for vaginal birth increased by 62.3 percent between 2008 and 2015, going from $1,617 to $2,625. The average deductible for cesarean birth increased from $1,532 to $2,640, a jump of 72.3 percent.

The standardized costs of maternity care remained about the same: $29,518 in 2008 compared to $29,314 in 2015. So the average share of maternity costs paid by patients rose from 12.3 percent in 2008 to 19.6 percent in 2015.

The average deductible payment for vaginal birth increased by 62.3 percent between 2008 and 2015. The average deductible for cesarean birth jumped 72.3 percent.

Legislation to establish policies restricting cost-sharing for maternity care may be needed to rein in prices for pregnancy care. As Moniz, an assistant professor of obstetrics and gynecology at the University of Michigan, points out, “Maternity and childbirth care are essential health services that promote the well-being of families across our country. Reducing patients’ costs for these high-value services makes sense.”

The study is published in Health Affairs.