Abortion bans successfully prevented some women from getting abortions in the immediate aftermath of the Supreme Court’s overturning of Roe v. Wade, according to a detailed new study of birth data from 2023. The effects were most pronounced among women in certain groups — Black and Hispanic women, women without a college degree, and women living farthest from a clinic.

Abortion has continued to rise since the period the data covers, especially through pills shipped into states with bans. But the study identifies the groups of women who are most likely to be affected by bans.

For the average woman in states that banned abortion, the distance to a clinic increased to 300 miles from 50 miles, resulting in a 2.8 percent increase in births relative to what would have been expected without a ban.

For Hispanic women living 300 miles from a clinic, births increased 3.8 percent. For Black women, it was 3.2 percent, and for white women 2 percent.

“It really tracks, both that women who are poorer and younger and have less education are more likely to have an unintended pregnancy, and more likely to be unable to overcome the barriers to abortion care,” said Dr. Alison Norris, an epidemiology professor at Ohio State who helps lead a nationwide abortion counting effort and was not involved in the new study.

The working paper, released Monday by the National Bureau of Economic Research, is the first to analyze detailed local patterns in births soon after the Dobbs decision in 2022, a period when abortion was declining or about flat nationwide.

Unexpectedly, abortions have increased nationwide since then. Researchers say this is evidence of unmet demand for abortions before Dobbs. Since then, telehealth and a surge in financial assistance have made it easier for women to get abortions, in both states with bans and where it remained legal.

But the new findings suggest that the assistance didn’t reach everyone. State bans appear to have prevented some women from having abortions they would have sought if they were legal.

The national increase in abortion masks that some people were “trapped by bans,” said Caitlin Myers, a professor of economics at Middlebury College and an author of the paper with Daniel Dench and Mayra Pineda-Torres at Georgia Tech. “What’s happened is an increase in inequality of access: Access is increasing for some people and not for others.”

The rise in births was small, suggesting that most women who wanted abortions had still gotten them, said Diana Greene Foster, the director of research at Advancing New Standards in Reproductive Health at the University of California at San Francisco. Still, she said, the new study was persuasive in showing the effects of bans: “I now feel more convinced that some people really did have to carry pregnancies to term.”

John Seago, the president of Texas Right to Life, said that a federal abortion ban would work better than a patchwork of state policies, and that states like Texas needed to do more to reduce out-of-state travel and mail-order abortion pills. But he did think Texas’ law was making a difference.

“We obviously are seeing the evidence that the bans are actually preventing abortions,” he said. “They’re actually saving lives.”

Previous studies have measured changes in the abortion rate, but Professor Myers said looking at the number of babies born is the most definitive way to know whether abortion bans actually work. Research from the years before Roe was overturned showed that longer distances from clinics affected abortions and births.

“This is the paper I’ve been waiting to write for years,” she said. “These are the data I was waiting for.”

The data she wanted was detailed birth certificates filed in 2023. Mothers include information about their age, race, marital status, level of education and home address in nearly every state, making demographic comparisons possible. The researchers used a statistical method that compared places with similar birthrates before Dobbs to estimate how much a ban changed the expected birthrate.

They also used county-level data to look at changes in births within states. In counties in states with bans where the distance to the nearest clinic in another state didn’t change, births increased 1 percent. In counties where the distance increased by more than 200 miles, births increased 5 percent.

In Texas, the largest state with an abortion ban, births increased more in Houston, where the nearest clinic is 600 miles away in Kansas, than they did in El Paso, where the nearest clinic is 20 miles away in New Mexico. Similarly, births increased more in the South, where states are surrounded by other states with bans, but very little in eastern Missouri, where there are abortion clinics across the border in Illinois.

The researchers also looked at appointment availability at nearby clinics, because some clinics have been overrun with people traveling from other states. They found that if women were unable to get an appointment within two weeks, births increased even more.

Still, even in places with bans that had no change in distance to the nearest clinic or appointment availability there, relative births increased slightly, which Professor Myers attributed to “a chilling effect” of bans.

The findings are in line with other research. A previous analysis, using state-level data through 2023 and a different statistical method, found that births increased 1.7 percent, and more among women who were Black or Hispanic, unmarried, without college degrees, or on Medicaid.

“Using different methods, using slightly different data, we’re coming to the same conclusion about the disparate impacts of these policies on populations,” said Suzanne Bell, a demographer at Johns Hopkins and an author of that paper. “I think that’s adding further evidence to the notion that these are real impacts that we’re capturing.”

Since the study’s county-level data ends after 2023, it’s possible that births in states with bans have decreased since then. Abortions nationwide have continued to increase, including for women in states with bans.

Doctors in states that passed so-called shield laws, which protect them from legal liability if they send pills into states with bans, began doing so in earnest during the summer of 2023. Abortions done this way would not affect birth data until 2024.

But using provisional state-level birth data from 2024, the new paper found almost no change in births from 2023. This data is less reliable, but researchers said that even with shield laws, some women are still unlikely to get an abortion — especially those with fewer resources, who may not know about telehealth abortion sites or are wary of ordering pills online.