Yes they can do it. But it would involve making a hole in the amniotic sac... which is very unsafe, it's a risk of infection, and the amniotic fluid could leak. I would also imagine it's pretty costly, and I don't think insurance companies would cover it because it's unnecessary. I would wait until your baby is born, it's too much of a risk, and the wait wont be as long as you think it is... the baby will be here before you know it, and then the DNA test is absolutely harmless, just a little swab in the mouth.