I googled it and only found one other person (who basically said the same thing as OP. When I googled Center for Medical Genetics, it sent me to this website, which talked about their prenatal gender test:
http://www.geneticstesting.com/gendertest/gendertest.htm
They don't give any specifics, and say to call for details, but it appears they allow you to do it through the mail? Not sure...