Infanticide

Infanticide has been a custom of human societies for thousands of years. Infanticide simply put is the killing of an infant. There are records of infanticide dating far back in the historical record. We have records of the practice in Africa, Asia, Europe, Australia, North America, and South America. The practice is known to have continued into the middle ages, and even into the modern day but is no longer a commonly accepted practice throughout the majority of the world.
Infants were sacrificed to various pagan gods in several world religions and cultures. One example is the worship of the Ammonite god Molech. An idol of Molech would be made of metal, have outstretched arms in which to place an infant and a hollow base in which a fire would be built. When the idol was red hot the infant would be placed in the hands of the god. The Israelites were specifically commanded to have no part in the worship of Molech.

Leviticus 20:2-5
You shall also say to the sons of Israel: Any man from the sons of Israel or from the aliens sojourning in Israel who gives any of his offspring to Molech, shall surely be put to death; the people of the land shall stone him with stones. I will also set My face against that man and will cut him off from among his people, because he has given some of his offspring to Molech, so as to defile My sanctuary and to profane My holy name. If the people of the land, however, should ever disregard that man when he gives any of his offspring to Molech, so as not to put him to death, then I Myself will set My face against that man and against his family, and I will cut off from among their people both him and all those who play the harlot after him, by playing the harlot after Molech.

When the Lord, speaking through Jeremiah, listed the reasons why Judah was to be sent into captivity the worship of Molech was specifically listed.

Jeremiah 32:35
They built the high places of Baal that are in the valley of Ben-hinnom to cause their sons and their daughters to pass through the fire to Molech, which I had not commanded them nor had it entered My mind that they should do this abomination, to cause Judah to sin.

In Rome, Greece and other societies infanticide was practiced via exposure as a form of economic convenience, family planning, and for other reasons. After birth the child would be presented to the father and he would decide whether the child would be raised or left out in the elements to either die or be picked up by another family. The decision would often be based on whether or not he felt that he could support the child in a financial manner he deemed acceptable. Other times the decision would be based on the gender of the child, often selecting for males, but sometimes for females.

Oxyrhynchus, Egypt, 1 B.C. (Oxyrhynchus papyrus 744. G)
A letter from a husband to his wife directing her not to raise her baby if it is female. Exposed children were left to be raised by others or to die.
“Hilarion to Alis his sister, heartiest greetings, and to my dear Berous and Apollonarion. Know that we are still even now in Alexandria. Do not worry if when all the others return I remain in Alexandria. I beg and beseech of you to take care of the little child, and as soon as we receive wages I will send them to you. If-good luck to you!-you bear offspring, if it is a male, let it live; if it is a female, expose it. You told Aphrodisias, ‘Do not forget me.’ How can I forget you? I beg you therefore not to worry.”
The 29th year of Caesar, Pauni 23.

The Spartans of Greece would examine a newborn child for defects and leave those found lacking out in the elements to die. In some regions twins were deemed as unlucky and would be put to death.
Today it is thought that the rates of infanticide worldwide have dropped to 2.1 per 100,000 newborns annually. While we don’t have firm numbers for the rates of infanticide throughout ancient history and the middle ages this rate is considered to be much reduced from previous levels. This shift has occurred largely due to a shift in peoples minds recognizing newborns as people, and therefore infanticide as murder.
In the US there were an estimated 1.21 million legal abortions performed in 2008. Idaho had the lowest abortion to live birth rate at 59 abortions per 1000 live births. NYC had the highest reported rate at 732 abortions per 1000. Twenty two percent of all US pregnancies end in abortion. In 2000 about 2,200 partial-birth abortions were performed in the US, or about 200 cases per 100,000 newborns.

References:
http://www.abort73.com/abortion_facts/us_abortion_statistics/
http://www.npr.org/2006/02/21/5168163/partial-birth-abortion-separating-fact-from-spin
http://en.wikipedia.org/wiki/Infanticide