Two US states have banned child marriage this month, but experts warned rising use of online marriage licenses during the coronavirus pandemic could weaken protections in a country where it was legal everywhere less than two years ago.
Be it to hide pregnancy or follow religious tradition, tens of thousands of girls - some as young as 12 - marry older men in the United States each year, campaigners say.
During the pandemic, several US states including New York have allowed couples to make remote marriage applications and clerks to perform ceremonies via video conference.
Campaigners who have sought to end child marriage in the United States said that could make coercion of young brides harder to spot and proof of age easier to fake.
"Many states' laws already can be manipulated by abusive parents, exploitative parents, opportunistic predators," said Jeanne Smoot, senior counsel at the Tahirih Justice Center, which opposes child marriage.
"Going virtual makes us all the more concerned," she told the Thomson Reuters Foundation. "Those risks could be ratcheted up at this time."
Globally 12 million girls marry under 18 every year, says Girls Not Brides, a coalition working to end child marriage which the United Nations regards as a human rights violation.
Campaigners say children married young are more likely to leave school, get divorced, experience domestic abuse and mental health problems and live in poverty than those who marry later.
Most are in the developing world, but child marriage is legal in all but four of the 50 US states. Pennsylvania and Minnesota banned the practice just this month.
The Pennsylvania measure also initiated a system for couples to apply for a marriage license remotely during the health crisis.
State Rep. Jesse Topper, a sponsor of the Pennsylvania bill, said he did not consider the remote option as a potential avenue for underage brides or grooms to pass unnoticed.
"I just simply don't see that as being an issue," he said. "Obviously, if you're caught lying or breaking the law in that way, that certificate will be void."
About one in 200 children aged 15 to 17 - some 58,000 - were married in 2014, according to a Pew Research Center analysis of USCensus Bureau data, the latest information available.
Survivors of child marriage often say they were forced to marry against their will, particularly if they were pregnant to avoid the stigma of giving birth outside wedlock. Religious and cultural traditions also foster an increase in young brides.
Fraidy Reiss, head of the Unchained At Last advocacy group, said an unambiguous ban nationwide on marriage for anyone under 18 was the only way to end the abuse.
"I've worked with survivors who showed up at the clerk's office sobbing and begging for help, and there was nothing the clerk could do or the clerk didn't even notice," she said.
"Even in person, these girls are not getting the help that they're begging for."