> I used to live in a state where some new friends had told us about places that facilitated pregnant women's trips to the US solely for the purpose of staying and giving birth in the US so the child could become citizens. They then head home. I have no idea how prevalent this is.

As many as 26,000 mothers do it (birth tourism) every year.

CIS analyzed U.S. Census Bureau data to track the number of foreign-born mothers who gave birth in the United States. Researchers cross-referenced those births against federal figures of temporary visitors. They isolated foreign mothers who arrived on short-term visas, gave birth, and did not establish long-term residency in the U.S. CIS concluded that 20,000 to 26,000 births annually are attributable to women arriving on short-term tourist visas specifically to obtain citizenship for their children.