Congrats? I know you are emotional right now..
I was drinking when I found out I was preggo at 8 weeks. I quit. I am not trying to upset you but your age makes the risk factor for birth defects go up. After 35, it increases each year. There are tests that can be performed for birth defects, you need to talk to your doctor. Some tests cannot be done after 15 weeks because the results are not reliable.
You may want to see a perionatologist that specializes in high risk births, you may be referred to one due to your age anyway. He can do an amino if you are really worried.
Be SURE you are taking B vitamins. A lot of birth defects are caused by a lack of B vitamins, especially folic acid. Your first trimester is most critical because the neural tube closes, I think around 12 weeks.
Be honest with your doctor. My baby girl was fine but I did quit once pregnancy was confirmed. I had bad morning sickness and alcohol didn't interest me at all. Good luck!