You are still young. Chances of your child being born with birth defects is highly unlikely. Just do all you can to keep yourself and that baby healthy, such as the proper diet.
In the meantime, don't dwell on the "what if's." That's all these fears are, and "what if's" hardly ever materialize. Bask in the joy and anticipation of your new arrival and thank God every day for this wonderful new life that is about to enter the world.