Prenatal DNA test using only the mothers blood and the fathers saliva?

there is a website that says after 13 weeks of pregnancy they can do an accurate prenatal DNA test using the mothers blood.. do you think this is possible? they say that the mothers blood has the babies DNA floating around in it for some reason... and that they can do a DNA test from it. every other DNA test that is prenatal involves an amnio or a CVC test.. hmm what do you think?