The number of women and girls in the United States at risk of female genital mutilation has tripled over the last 25 years, according to a government study released on Thursday.

The last official estimate of how many people were affected by the practice was published in 1990. Since then, the number of women and girls at risk has jumped from 168,000 to 513,000 in 2012, said a highly anticipated study by the US Centers for Disease Control and Prevention.

It is unclear how many women and girls in the US have undergone the procedure.

Jaha Dukureh, who has helped lead the US campaign against FGM, said she was happy that the results had finally been published. She launched a campaign for the government to commission such a report in May 2014 with the backing of the Guardian and UN secretary general Ban Ki-moon.

“I’m not really surprised because I’ve seen these numbers before and it just means that government needs to do more when it comes to education and outreach in these communities,” Dukureh said.

Unpublished data from the CDC seen by the Guardian in February 2015 estimated that the amount of women affected had grown to 513,000. And the nonprofit Population Reference Bureau (PRB) said that month that about 507,000 women were affected by the practice.

The US government outlawed FGM in 1996 but some people send their daughters to countries that permit the practice for “vacation cutting”, FGM which is also illegal in the US.

Dukureh was mutilated as a child in the Gambia, where she was born. She held a youth summit on the practice there in October 2015. The Gambia president Yahya Jammeh banned the practice the following month.

The CDC said that the increase in women at risk in the US was “wholly a result of rapid growth in the number immigrants” from countries that practice FGM.

And the risk for girls in the US younger than 18 has grown fourfold, said the study.

“It’s the 21st century and I think no one should be forced to be go through something like this,” Dukureh said. “No child should be forced to undergo this.”

Shelby Quast, Americas director of Equality Now, which aims to end the practice worldwide, said that these numbers are an important resource for campaigners to push for policy change.

“We advocated for – and got – an inter-agency working group to address FGM in the US,” Quast said in an emailed statement. “But the US needs to continue to step up and take charge. This means implementing the law on FGM more effectively, but that also includes training professionals who come in contact with girls at risk or survivors, including health care workers, teachers and social workers.“

The study’s authors wrote that the “ultimate goal” of collecting this data “should be to contribute to preventing the practice and providing services to those who have undergone it.”

The authors wrote: “By implementing actions to capture information that enhances knowledge on those issues, the United States can more effectively move toward prevention.”