With the advance of pre-natal 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 pre-natal 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, pre-natal 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 England, those percentages are even higher.
In some places (areas of rural China and India, for example, see US Census Bureau Reports on 'Son Preference' in Asia), '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 Ohio, legislators proposed their own PRENDA (Prenatal Non-Discrimination Act) legislation. This bill would make it an offense, punishable by up to five years imprisonment, to knowingly do any one of the following: (1) perform an abortion "knowing that such abortion is sought based on the sex or gender of the child"; (2) use "force or threat of force...for the purpose of coercing a sex-selection abortion"; or (3) solicit or accept funds to perform a sex-selection abortion.
 Susan W. Enouen, "Down Syndrome and Abortion," physiciansforlife.org, Physicians for Life, Web. 24 July 2012, <http://www.physiciansforlife.org/content/view/1301/26/>.