Screening DNA when choosing embryos don't always result in favor of the parents. Researchers say that DNA predictions of height or IQ might help parents select an embryo that may grow into a child who is at most about 3 IQ points smarter or 3 centimeters taller than the average embryo. Offspring that were predicted to have a certain trait often possessed the opposite. There is a procedure known as the Preimplantation Genetic Diagnosis(PGD) which is used to create embryos through in vitro fertilization. This would give couples the opportunity to screen out embryos carrying a disease causing DNA variant.
Source 1: https://www.sciencenews.org/article/why-screening-dna-designer-babies-probably-will-not-work
Source 2: https://americanpregnancy.org/getting-pregnant/preimplantation-genetic-diagnosis-pgd/