Updated

The 14-week-old twins a pregnant Laurie Thompson is carrying don’t belong to her. Conceived with donor eggs, they are the children of a same-sex couple from Spain who turned to Thompson because paid surrogacy is illegal in their country, the Detroit Free Press reports.

"There's such pride in knowing that I did this for somebody," Thompson says of her experience as a surrogate, which also has included a pregnancy for a married couple from Serbia.

In the past five years, would-be parents from as far as Istanbul and Uruguay have turned to healthy, young American mothers to serve as surrogates, according to the Detroit Free Press.

The babies are born U.S. citizens, but surrogacy agency officials say that's not a primary motivation for the parents, who typically come from European and Latin American countries where surrogacy is illegal or socially unacceptable. The parents have exhausted other options and are willing to pay about $50,000 to $100,000 -- part of which goes to the surrogate -- to have biological children.

No one tracks how many of the estimated 1,400 babies via surrogacy in the U.S. each year are for international parents, but one of the larger U.S. agencies, the Center for Surrogate Parenting in Encino, Calif., estimates that about half of its 104 births in 2010 were for international parents, the paper reports.

In Illinois, which has one of the most surrogacy-friendly laws in the nation, at least two dozen international babies were born to surrogates in 2010. The other states that explicitly allow contracts for paid surrogacy are Arkansas, California and Massachusetts.

Click to read more about international couples using U.S. surrogates from the Detroit Free Press.