It's simply a way of obtaining information ahead of time. Leaving everything about your child purely up to chance is absurd, especially if there's a reliable and safe way to find out a bit about it before you're forced to deal with problems you could have avoided. In fact, one could even make a rather strong argument that not making use of this testing, if able, is in fact unethical. It simply does not make any sense to say that the practice of looking at your potential future child's DNA is unethical. If your child is perfectly healthy, no worries. If, however, it would grow up with a permanent, pervasive genetic disorder that would have an enormous negative impact on it's life, you're better off finding out early, so that you can at least prepare, or, if you'll excuse the language, scrap it and try again. The only way this could possibly be considered unethical is if a connection is made to abortion-due-to-gender, which is a cultural problem and not one of the technology itself, thus not an issue to be considered here.
Parents have the right to know ahead of time if their newborn will have genetic abnormalities. Even if abortion isn't an option for the couple, it gives the parents time to prepare for possible medical bills once the baby is born. Knowing is half the battle. There is nothing wrong with fetal genetic testing, anymore than the mother can eat and drink what she wants while the baby is the womb.
It prevents a lot of problems with in the family. There are so many things that come along with raising a special needs baby and not everyone is ready to take that on. You have extra financial needs, time needs, as well as schooling needs. It should be up to each individual weather they do it or not.
In my view, it is ethically wrong to test a product on an innocent human. An innocent animal, I'm okay with. A guilty human, less okay with but it'll do for the greater good. An innocent human, that's taking it one step too far.
I don't agree with abortion. Testing on fetuses isn't any better. If we're using humans like objects for testing, then there is something wrong with society. We're supposed to have a respect for each other and life. By testing on a fetus, we're disregarding it, and that's just wrong. Fetuses shouldn't be tested on.