Tammi Kromenaker runs the Red River Women’s Clinic, the only clinic that provides abortions in North Dakota. Without Roe v. Wade, the Supreme Court decision that established a constitutional right to abortion, the state would ban her clinic, or any other within state lines, from performing the procedure.

“Roe is the only thing keeping abortion legal in North Dakota,” Kromenaker said.

In neighboring Minnesota, though, abortion would remain legal, even without the protection of Roe. There, the right to abortion is protected in the state constitution.

Roe upholds abortion in very different ways around the country. Without it, the fallout would be highly uneven, according to new research by scholars at Middlebury College and two reproductive health research groups.

Today, there is at least one abortion clinic in every state, and most women of childbearing age live within an hour’s drive or so of one, the new analysis found. In more than half of states, including the entire West Coast and Northeast, that would still be true without Roe. In other states, like Missouri and Mississippi, with one clinic each, some women are effectively already living without Roe’s protections, because the driving distance to the nearest clinic is prohibitively long.

Without Roe, significantly more women — concentrated in the South and Midwest — would be living without an abortion clinic nearby: Eight states have passed trigger laws that would ban abortion almost immediately, and at least 13 more states would probably ban it, legal experts say.

The nation’s abortion rate would be at least 13% lower without Roe v. Wade, the new analysis found. In some counties, it would be more than 40% lower. There could be 140,000 fewer abortions a year, it found. Low-income people who couldn’t afford to travel to a legal clinic would be most affected.

“Wide swaths of the country face potential dramatic increases in travel distances to states where abortion would likely remain legal,” said Caitlin Knowles Myers, an economist at Middlebury and one of the paper’s authors. “Affluent women generally find a way to get there, but 75% of abortion patients are poor or near-poor.”

The estimates in the new paper are based on two elements: research of how recent clinic closings in Texas affected abortion rates among women whose driving distance to providers increased; and two sets of assumptions about which states might outlaw abortion if Roe were overturned.

The current Supreme Court is considered unlikely to overturn Roe immediately, but changes on the court and state actions limiting or trying to ban abortion have spurred advocates and providers, including Planned Parenthood, to begin planning for a post-Roe world.

Eventually, clinics might open on state borders so women in states with abortion bans could more easily reach them, researchers and women’s health experts say, and an underground market for abortion-inducing pills could arise.

But in some parts of the country, abortion rates would fall almost instantly.

It would still be possible to cross state lines to get an abortion. But as distances increase, abortion rates decline.

Missouri has one abortion clinic, in St. Louis. Without Roe, it would close, but driving distances wouldn’t greatly change, since a clinic in Illinois, where abortion is protected by a state statute, is about 10 miles away.

In Louisiana, by contrast, the estimates suggest that abortion rates would drop sharply. That’s because several neighboring states also have trigger laws, meaning the nearest clinic could be hundreds of miles away.

In other states, abortion clinics wouldn’t close immediately, but legal experts at the Center for Reproductive Rights say 21 states would most likely move quickly to restrict or ban abortion. Their assumptions are based on analysis of historical and recent legislative action in those states and, in some cases, on state court rulings.

Alabama, for example, recently passed a law that would criminalize nearly all abortions. The law is unlikely to go into effect for now because it clearly conflicts with Roe. But its passage suggests the state government is committed to that policy goal.

Even if Roe were struck down, abortion access would remain unchanged in large regions of the country.

“I don’t think anyone in Massachusetts is going to find any difference in their life as a result,” said Phillip Levine, an economist at Wellesley College and a leading researcher on the topic. “But if you’re in Arkansas or Nebraska, if you don’t have means, it’s going to be virtually impossible for you to get an abortion legally.”

This state variation is a leading goal of abortion opponents, said Clarke Forsythe, senior counsel at Americans United for Life. “The blue states can legislate according to public opinion in the blue states, and the red states can legislate according to public opinion in the red states,” he said.

Today, 83% of women of childbearing age live within 50 miles of an abortion clinic, found the new paper, which has not yet been published. Without Roe, if all 21 states that have indicated intentions to make abortion illegal did so, about half of women this age would live that close to a clinic, and a quarter would live more than 200 miles from one.

Long travel distances are most likely to affect low-income women, research has found. These women, who account for a growing share of abortions, might have a harder time arranging and paying for transportation and child care, and taking time off work.

Women who could not get to an abortion clinic would not necessarily give birth. Some women miscarry. Many might turn to alternate ways of ending their pregnancies, researchers said. Two pills that end a pregnancy of up to 10 weeks, mifepristone and misoprostol, can be administered at home. Although medication abortion would be illegal in states that banned abortion, the pills could be clandestinely driven or mailed across state lines.

In Texas, researchers were unable to count how many people found illicit ways to get an abortion, like traveling to another state or taking the pills, but the birthrate did not rise in tandem with the decrease in abortion, and in-clinic abortion rates declined the most sharply in counties along the border with Mexico, where one of the pills is sold over-the-counter as an ulcer medicine.

“Our best guess is that for people who didn’t give birth, they were going to other sources for abortions,” said Corey White, an economist at Cal Poly and a co-author of another paper on Texas clinic closures.

Illegal abortions might be more easily accessible and safer than they were pre-Roe, reproductive health researchers and historians say. But they warn that some women might still seek dangerous methods if legal abortion were curtailed and enforcement of laws were strict.

Over time, some people might practice abstinence or safer sex because of the knowledge that an abortion would be harder to obtain. Also, abortion providers would probably open new clinics in places that women in states without clinics could more easily reach.

In North Dakota, Kromenaker has already made contingency plans. Fargo, where her clinic is based, is only a few minutes from the Minnesota border, where abortion would remain legal. She said she would keep her clinic open, providing patients with pre-abortion care and other services, and open an abortion clinic across the border.

“Folks across the country are already working on these plans in these haven and hostile states,” Kromenaker said.

But in some areas, the nearest state with legal abortions may be too far to make an easy trip feasible. Also, existing clinics might be unable to meet an increase in demand. In Texas, just more than half the decrease in in-clinic abortions was because of overcrowding and wait times, the researchers found. Some women might have forgone abortions, turned to alternate methods or had second-trimester abortions as a result, they said.

The new nationwide analysis did not factor in overcrowding, so the decrease in the abortion rate would almost surely be higher than estimated, at least until clinics added capacity. “These maps are very conservative, all based on the assumption that once women get there, the provider can see them,” said Myers, the Middlebury economist. “That’s not necessarily going to be true.”

The paper’s other authors are Ushma Upadhyay, an associate professor at Advancing New Standards in Reproductive Health, a research group at the University of California, San Francisco, and Rachel K. Jones, a sociologist at the Guttmacher Institute, a research group that supports reproductive rights. Myers has been paid by abortion rights groups as an expert witness.

There are other signs suggesting that what happened in Texas might not be an entirely accurate forecast of what would happen elsewhere in the country if Roe were overturned.

Abortion was not banned in Texas, and the law that forced some clinics to close was eventually overturned. Texas is a big state with a mix of urban, suburban and rural areas, but is not a microcosm of the nation. In some of rural America, abortion rates could fall less than they did in Texas, because people are used to driving long distances, whether for shopping or medical care. In other places, rates could fall more because the distances to the nearest clinic could grow even larger, or winter weather would make long-distance travel more treacherous.

Calla Hales, who runs four abortion clinics in North Carolina and Georgia, said her patients travel 2 1/2 hours on average. It can be a formidable challenge, even with Roe in place.

“As it is now, there are patients who don’t get their intended abortions due to financial and logistical hardships,” Hales said. “The fall of Roe would absolutely increase this.”

This article originally appeared in The New York Times.