Roughly 33,000 United States-born children are delivered to foreign women who arrived in the country on tourist visas, new estimates reveal.

Estimates published by the Center for Immigration Studies’ Director of Research Steven Camarota find that about 33,000 U.S.-born children are delivered to tourist visa-holders annually. These children are often referred to as “anchor babies,” as they are given birthright American citizenship despite their parents’ either being illegal aliens, temporary foreign workers, or temporary foreign visitors.

Camarota’s research is taken from national birth certificate records and U.S. Census Bureau data.

The estimates provide a look into the massive birth tourism industry in the U.S. just as President Trump is reportedly planning a crackdown.

Under a new rule, the Trump administration may soon order consular officers to review whether applicants for B-1 and B-2 visas are simply attempting to come to the U.S. in order to deliver a baby and secure that child birthright American citizenship.

To date, the U.S. Supreme Court has never explicitly ruled that the U.S.-born children of illegal aliens must be granted automatic American citizenship, and a number of legal scholars dispute the idea.

Many leading conservative scholars argue the Citizenship Clause of the 14th Amendment does not provide mandatory birthright citizenship to the U.S.-born children of illegal aliens or noncitizens, as these children are not subject to U.S. jurisdiction as that language was understood when the 14th Amendment was ratified.

For almost two years, Trump has signaled that he has reviewed signing an executive order to end birthright citizenship, otherwise known as the “anchor baby policy.” That executive order, though, has yet to come up for consideration.

Today, there are at least 4.5 million anchor babies in the U.S. under 18, exceeding the annual roughly four million American babies born every year and costing American taxpayers about $2.4 billion every year to subsidize hospital costs.

John Binder is a reporter for Breitbart News. Follow him on Twitter at @JxhnBinder.