Surprise, it’s a girl! And an out-of-network bill you weren’t expecting!

Pregnancy and childbirth can cost thousands of dollars, even when the doctors and services are covered by insurance. But surprise out-of-network bills add to the tab for many women, according to a study by researchers at the University of Pennsylvania and University of Missouri Kansas City published in the March issue of Health Affairs.

Researchers analyzed a national sample of medical claims for 63,630 women with employer-sponsored health insurance who gave birth twice between 2007 and 2014. About one in 10 mothers experienced a surprise out-of-network bill with their first delivery. Those who did were more likely to switch providers for their second delivery.

Surprise bills happen when patients go to a hospital that is in their insurance network but are treated by a doctor there who is not part of the network. These bills are often unavoidable, and although some states, including New Jersey, have passed laws to protect patients, many are left with no choice but to pay up.

“Patients seeking care have a lot going on — they’re figuring out how to get better, what care they need, what the recovery process is going to be like. A surprise bill they didn’t know about — couldn’t possibly know about — just adds insult to injury,” said Benjamin Chartock, an associate fellow at the Leonard Davis Institute of Health Economics at the University of Pennsylvania and the study’s lead author.

A woman who chooses an in-network hospital and obstetrician for her labor and delivery could end up with a surprise bill if one of the other providers who treats her -- for example, the anesthesiologist who administers an epidural -- is not employed directly by the hospital, Chartock said.

Surprise bills are also common in emergency departments, which may be staffed by doctors on contract, rather than employed by the hospital. Doctors employed by a hospital are typically bound by the hospital’s insurance contracts.

Researchers chose to study surprise bills among births as a way to analyze how such bills may influence future decision-making.

In an emergency, patients don’t have time to shop around. But for most births, patients have the ability to plan and choose where to receive care.

“If someone gets a surprise out-of-network medical bill, they’re powerless to respond in that episode of care. But for future episodes of care, they do have a choice — they can switch facilities,” Chartock said.

About 19 percent of women who received a surprise bill after their first birth switched hospitals for their second birth, compared with 16 percent of women who didn’t get a surprise bill.

Hospitals in the U.S. charged an average of $12,290 for a vaginal birth and $16,907 for a C-section in 2017, according to FAIR Health, a nonprofit that tracks health-care prices.

For women with health insurance, coverage for pregnancy and childbirth is considered an essential benefit that most plans are required to offer at no additional cost to members.

But what exactly counts as an “essential” benefit varies, and it’s common for families to spend their deductible and even meet their out-of-pocket maximum on ultrasounds, tests, and other services that aren’t covered in full by their plan.

Women who experience a miscarriage similarly can be left with hefty bills to pay.

The study’s authors concluded that surprise bills are an unnecessary burden at an already stressful time and that laws protecting patients from unavoidable surprise bills could help.

Several states, including New Jersey, have established rules that hold patients harmless from surprise bills, instead requiring the doctors and insurers to work out a deal. Pennsylvania is among the states that have considered — but have not passed — such protections.