Indiana Gov. Mike Pence listens to a question during a news conference, Tuesday, March 31, 2015, in Indianapolis. (AP Photo/Darron Cummings)

(Reuters) - A U.S. federal judge blocked an Indiana measure requiring women to have an ultrasound at least 18 hours before undergoing an abortion, saying that the mandate was unnecessary and a burden to low-income women.

The preliminary injunction, issued by U.S. District Judge Tanya Walton Pratt on Friday, was the result of a lawsuit brought last year by the American Civil Liberties Union (ACLU) on behalf of Planned Parenthood of Indiana and Kentucky against Indiana's Department of Health and local officials.

The Indiana ultrasound measure was part of a renewed push by abortion opponents in the United States to restrict access to the procedure.

"These burdens are clearly undue when weighed against the almost complete lack of evidence that the law furthers the State’s asserted justifications of promoting fetal life and women’s mental health outcomes," Pratt wrote in her 53-page ruling.

There are six Planned Parenthood locations that provide the ultrasound services, meaning women who do not live near the centers have to travel to reach them, which could be costly, Pratt wrote.

"For women faced with the already high costs of an abortion and a lack of means to afford them, the additional expenses of lengthy travel, lost wages, and child care created by the new ultrasound law create a significant burden," the ruling said.

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The ultrasound mandate was in a larger package of abortion restrictions signed into law last year by Vice President Mike Pence, who was serving as governor of the state at the time.

The Indiana State Department of Health directed questions to the attorney general's office, which did not immediately respond to request for comment.

The law took effect on July 1, 2016. Prior to that, women still needed an ultrasound to have an abortion, but the time frame of when it needed to happen was not specified.

Nine women were unable to undergo abortions because of the stricter ultrasound regulation, according to the ruling.

"This is a major victory for women in the state. It's a major victory for Planned Parenthood," Ken Falk, legal director at ACLU in Indiana, told members of the media at a news conference on Monday.

Some 25 U.S. states have laws regarding ultrasounds and abortions, but only three states require medical staff to display and describe the images, according to the Kaiser Family Foundation, a non-profit group focusing on health issues.

(Reporting by Timothy Mclaughlin in Chicago; Editing by Andrew Hay and Lisa Shumaker)