Let's say you're a fertility doctor advising would-be parents who have exactly two viable embryos ready for implantation. The parents want to implant only one embryo. This is not an uncommon scenario; more than 71,000 babies were born in the U.S. via assisted reproduction in 2016.
For several decades now, folks using in vitro fertilization (IVF) have also tested for the single genes associated with certain heritable genetic diseases (such as cystic fibrosis, Huntington's disease, or hemophilia) and chromosomal abnormalities (such as those that cause Down syndrome). Nearly three-quarters of Americans approve of this pre-implantation genetic diagnosis (PGD) testing for diseases that are fatal early in life, according to a 2015 survey in the Journal of Assisted Reproduction and Genetics, and two-thirds support it for conditions that cause lifelong disability, writes Ronald Bailey.
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