first of all, CONGRATULATIONS!!! how exciting to be pregnant for the first time!! www.askdrsears.com has LOTS of good information on everything. check out his books, the baby book is one i cant live without!
i dont know much about the tests or anything.. i (pregnant at 23 helped) just followed doctors orders, except the test for downs syndrome and stuff i denied because 1. i didnt care i was keeping the baby no matter what and 2. there was no reason my baby should have any problems, and he doesnt.
what i want you to know most of all is that God is in control. i dont know how you feel about religion or anything, but for me thats important.
you need to ask yourself this one important question. if you got a test result that lead you to believe that the child would be disabled... what would you do? im going to assume that you would be keeping the baby no matter what. so does it really even matter what the test results are?
what im trying to say is, if you feel like it, you can just go one with it like a normal pregnancy. im not saying to ignore instincts, or if the doctor has genuine concerns, but dont feel like you have to go out of your way to test for something that isnt going to make a difference to you one way or the other.
you have 2 choices. find out while you are pregnant if there is something wrong (some people feel that helps them better prepare) or trust God and let Him lead you and your pregnancy for better or worse. even though i had no reason to believe my pregnancy wouldnt be perfect, i still chose to avoid a test that wasnt going to change anything.
the other thing that i fear with these tests is the false positives. it can be pretty stressful and heartbreaking to find out your child might have a problem. however, there really isnt any guarantees, and you could worry yourself over nothing... or make a choice that you might not otherwise make if you knew there was nothing wrong. how many babies do you think are taken because of a suspected problem, and they turn out to have been fine ? probably more than anyone would like to admit. mistakes happen. however, i would choose to not know about it at all, and let the doctors take care of it when the baby is born.
do you know what i mean? basically, i dont think there are any tests that should be required of you, and you shouldnt feel that you have to do any tests at all. after all, the Lord blessed you with a pregnancy, He will take care of the outcomes.
bless you and your baby - i pray that everything will go well for you!