With the advance of prenatal testing, it is possible for pregnant mothers to know not only the gender of their unborn child but also many other physical characteristics. For example, a physician could determine if the unborn child has certain medical conditions - diseases, malformations, organ problems, etc. This kind of prenatal testing can be profoundly helpful in treating some conditions in utero or preparing parents and medical personnel for the birth of a child with potentially major medical challenges.
Unfortunately, in our abortion-on-demand culture, prenatal testing is also used on behalf of medicalized 'search and destroy' missions in which children with disabilities are identified and killed in the womb by the violence of abortion.
So-called 'selective abortion' takes several different forms. In the case of multiple births (twins, triplets, etc.), doctors sometime identify one or several of the 'weaker' children and kill them to 'reduce' the number of children born.
Abortion is also used eugenically to discriminate against and kill pre-born babies who are handicapped. When diagnosed prenatally, between 84% and 91% of Down's Syndrome babies are aborted in the United States. In Iceland, those percentages are even higher, nearly 100% of babies prenatally diagnosed with Down syndrome are aborted.
Ohio Right to Life was instrumental in the passage of Ohio's Down Syndrome Non-Discrimination Act, signed into law in December 2017. This legislation is currently in litigation, but when it goes into effect will prohibit an abortion from being performed on an unborn child on the basis of that child having Down syndrome. A study published by the National Center for Biotechnology Information and featured in the New York Times found that approximately 92% of unborn children diagnosed with Down syndrome are aborted.
In some places (areas of rural China and India, for example, see Disappearing Daughters), 'selective abortion' is being used to kill unborn girls who are aborted for reasons of gender discrimination. These are called 'sex selection' abortions.
In May 2012, Live Action exposed Planned Parenthood's performance of sex-selective abortions in the United States. This bust and the four that followed spurred legislative efforts to prohibit sex-selective abortions in some states.
 Julian Quinones and Arijeta Lajka, "'What kind of society do you want to live in?': Inside the country where Down syndrome is disapearing," CBS News, Web. 5 December 2018, <https://www.cbsnews.com/news/down-syndrome-iceland/>.