If the process is not done carefully, the embryo could be accidentally terminated.
Furthermore, the technology used is not 100% safe yet. It is only in the experimental stages at this point.
Parents may use this technology for superficial purposes; such as purposely seeking out a blonde haired, blue eyed baby for appearance concerns only.
Could create a gap in society. “Designer” babies would most likely be better looking, smarter, etc. This could create “classes” between designer and non designer babies.
Because the technology is so new, it is unknown whether genetically modifying the babies will effect the gene pool. This could cause difficulties later on throughout the baby’s family tree.
A baby cannot consent to having it’s body altered; therefore some do not believe it’s right as parents do not “own” their children.
Genes often have more than one use. For example, a gene that controls intelligence could also control anger management. You could end up with a genius, but very angry, child.
Geneticists are not perfect people and cannot 100% properly evaluate every gene. It is more than likely mistakes will be made.
Individuality will be slighted. Because most people will seek out good-looking, intelligent babies with other optimum characteristics, everyone will be relatively similar.