This video excerpt from NOVA examines a genetic screening technique called preimplantation genetic diagnosis, or PGD. PGD enables researchers to identify mutations in an embryo’s DNA that can lead to birth defects and more than 300 diseases, including Huntington’s, cystic fibrosis, and some cancers. While the technique allows parents who use in vitro fertilization (IVF) to better understand the risk that their child might be diagnosed with a terrible disease, it is also being used in some parts of the world to select for sex. Serious ethical questions are being raised about this use and about the possibility of expanding the list of traits that are screened for.

This video is available in both English and Spanish audio, along with corresponding closed captions.