Updated

As discussion over whether to end birthright citizenship intensifies, a new study of Census Bureau data reveals that 8 percent of children born in the United States in 2008 were parented by illegal immigrants.

The Pew Hispanic Center, a project of polling organization Pew Research Center, finds that, of the 4.3 million babies born in 2008, roughly 340,000 were born to undocumented aliens. This is double the percentage of illegal immigrants in the U.S., owing in part to the fact that the illegal immigrant population is largely comprised of men and women at birthing age.

In addition, high birthrates among undocumented aliens give that population a similar share of children in the U.S. The study finds that children born to illegal immigrants account for 7 percent of the total population of people under the age of 18, or 5.1 million children. Four million, or 79 percent, of those children were born in the United States, making them U.S. citizens.

This analysis comes amid calls from some GOP members to consider ending birthright citizenship, the right enshrined in the 14th Amendment, that persons born in the United States are citizens of the country and the state in which they reside. House Minority Leader John Boehner, R-Ohio, said on NBC's "Meet The Press" this week that terminating the practice is an idea "worth considering."

Ending or revising the guarantee of birthright citizenship, Boehner said, may eliminate a major motivation for many immigrants to cross the border unlawfully. "There is a problem. To provide an incentive for illegal immigrants to come here so that their children can be U.S. citizens does, in fact, draw more people to our country," Boehner said. "I do think that it's time for us to secure our borders and enforce the law and allow this conversation about the 14th Amendment to continue."

Critics of the idea claim that the guarantee their children will be U.S. citizens is not great enough of an incentive for parents to immigrate illegally, since they would have to wait 21 years for their children to be old enough to sponsor their parents for citizenship. Additionally, such a change would require a Constitutional amendment, which two-thirds of Congress would have to approve before state legislatures consider the measure, and three-quarters of those must agree to the provision for it to become part of the Constitution. A bill that calls for such a change-the Birthright Citizenship Act of 2009-has been stalled in the House since April 2009.

Meanwhile, half of respondents in a new poll support a Constitutional amendment ending automatic birthright citizenship. In a Fox News/Opinion Dynamics poll released today, 50% of respondents said they do not think a child born to an immigrant living in the U.S. illegally should automatically become a citizen.

The Pew study analyzed data from a March 2009 Current Population Survey, conducted by the Census Bureau. View the complete report here.