Some parents turn to these tests to avoid passing on devastating genetic disorders that run in their families. But customers of the companies emerging to provide it to the public may not be getting what they’re paying for. Preimplantation genetic testing (PGT), while still relatively rare, is not new. Since the 1990s, parents undergoing in vitro fertilization have been able to access a number of genetic tests before choosing which embryo to use. A type known as PGT-M can detect single-gene disorders like cystic fibrosis, sickle cell anemia, and Huntington’s disease.