You cold ask the same about Noah, or about any local population that ever experienced a genetic bottleneck. And the answer is that birth defects do not always result from inbreeding, especially if it is brief. Adam and Eve had many children (Genesis ch.5), which created a diverse population immediately. This, together with the fact that God gave them robust genetics to start with.
Overall we would loook similar to how Adam and Eve appeared. They, however, did not have an accumulation of genetic defects in their offspring, so inbreeding itself would not have been an issue. The only differences would be minor ones common to racial variations and the fact that Adam and Eve were genetically perfect.
You and your wife have had a child and you name him Adam, then Adam grows up and has two children that he and his wife named Cain and Abel. Cain and Abel are your grandchildren. When Cain and Abel grow up and have their own children, these children are your great grandchildren.
Adam and Jake
Edward Adam Romero
Adam and Eve had children with the reproductive powers God had given them. At Genesis 4:1 says: "Now Adam had intercourse with Eve his wife and she became pregnant. In time she gave birth to Cain..."
Adam Rodman's birth name is Rodman, Adam.
Adam Aldridge's birth name is Adam Spratt.
Erick Adam's birth name is Erickson Adam.
Adam Barrington's birth name is Adam Badrawy.
Adam Michnik's birth name is Adam Szechter.
Adam X's birth name is Mitchell, Adam.
Adam Wazyk's birth name is Adam Wagman.