A new study, billed as the first of its kind, makes those calculations state-by-state and county-by-county, revealing some striking disparities . In New York, the average distance is about three miles (five kilometers). At the other end of the scale, the average distance in Wyoming is about 168 miles (271 kilometers).
The analysis was conducted by researchers with the Guttmacher Institute, a research group that supports abortion rights, using 2014 data on abortion clinic locations and U.S. Census population figures. The findings were published online Tuesday by the journal Lancet Public Health .
Nationally, according to the study, half of all women of reproductive age lived within 11 miles (18 kilometers) of an abortion clinic in 2014. However, many women in rural areas lived much farther away; the study said 1 in 5 women nationwide would need to travel at least 43 miles (69 kilometers) to reach the nearest abortion clinic.
In the states with the longest average distance to travel - Wyoming, North Dakota and South Dakota - at least half of women of reproductive age lived more than 90 miles (145 kilometers) from the nearest clinic providing abortion services. Women in Alaska lived an average of nine miles (about 15 kilometers) from the nearest clinic, but 20 percent of women in that state would have to travel more than 150 miles (240 kilometers).
The researchers said the average distance increased between 2011 and 2014 for many women in Texas and Missouri, which imposed restrictions during that period that led to closure of some clinics. At one point recently, there was only one abortion clinic operating in Missouri; there are now two, and abortion-rights advocates are pursuing legal action to expand that number.
In a commentary in the journal, Ushma Upadhyay, a professor of obstetrics, gynecology and reproductive sciences at the University of California, San Francisco, detailed possible repercussions for women facing the long distances.
"Increased travel distance means increased costs for transport, overnight stay, lost wages from time off work, and childcare," she wrote. "For a woman who is economically disadvantaged, having to travel a long distance could put an abortion out of reach, leading her to carry an unwanted pregnancy to term."
Upadhyay suggested that access could be improved if nurse practitioners and certified nurse midwives were allowed to perform abortions without a physician's supervision. Another step, she wrote, would be for the Food and Drug Administration to lift restrictions on the abortion-inducing drug mifepristone so that women could get it at pharmacies with a prescription. It's now dispensed only at clinics, hospitals and doctors' offices.
The American Civil Liberties Union filed a lawsuit on Tuesday challenging those FDA restrictions.