History of Infanticide
Ancient Greece & Rome
The Greeks considered infanticide barbaric, but instead of outright killing their babies, they practiced exposure . Exposure would be just leaving the child….it was not considered murder because a passerby or a God could take pity on the child and save it .
In Rome, exposure was common, in a letter from a man to his wife during 1 BC he says:
"I am still in Alexandria. ... I beg and plead with you to take care of our little child, and as soon as we receive wages, I will send them to you. In the meantime, if (good fortune to you!) you give birth, if it is a boy, let it live; if it is a girl, expose it." 
Another option would be to take the child to the family patriarch and they would decide whether the child should be killed or left to exposure. Usually babies with birth defects were killed. By 374 AD infanticide was illegal in Rome, but offenders were rarely ever prosecuted.
Pagan European Tribes
German tribes also practiced a similar exposure to unwanted children. Many were left in the forest without food….this was especially common for children born out of wedlock. 
Christianity abhorred infanticide. In Apostles it was written, “You shall not kill that which is born” . In 318 AD Constantine I felt that infanticide was a crime. In 374 AD Valentinian stated that people must rear all children. The Council of Constantinople issued that infanticide was murder and in 589 AD the Third Council of Toledo worked on ending the Spanish custom of killing their children .
Child sacrifice was common among the Gauls, Celts, and Irish. "They would kill their piteous wretched offspring with much wailing and peril, to pour their blood around Crom Cruaich", a deity of pre-Christian Ireland .
But soon abandoning children on the doorsteps of churches and abbeys became more common than exposure. This gave birth to the worlds first orphanages.
In the Qur’an infanticide is forbidden. But before Islam, infanticide was practiced as “post partum birth control. Infanticide was practiced either out of destitution (thus practiced on males and females alike), or as sacrifices to gods, or as "disappointment and fear of social disgrace felt by a father upon the birth of a daughter". 
Marco Polo wrote about seeing many babies exposed in Mani . Sex Selective infanticide was common in China. Han Fei Tzu, a Chinese philosopher in the 3rd century BC wrote that
“As to Children, a father and mother when they produce a boy congratulate one another, but when they produce a girl they put it to death” .
Many Chinese tribes practiced infanticide by putting the baby into a bucked of cold water, called “baby water”  .
Infanticide was called “mabiki” which means to pull plants from an overcrowded garden. Mabiki was still practiced in the 19th and early 20th centuries. 
Children were killed if they were believed to have brought bad luck. So more often than no, twins were murdered because they were considered to be bad omens. Also if a parent died during childbirth, the baby would be buried alive. 
Why do people practice Infanticide?
Cultural prejudices and practices are hard to break and looking back into history it is easy to see why the killing of children has been considered normal.
Usually it has been because of economic problems. In times of famine, families would practice infanticide. Due to cultural norms where the need for a son a paramount, daughters are considered a burden because they cannot support families as easily as sons can. A daughter can be a liability and for poverty stricken families the price of a daughter in regards to a dowry can be too much. As one Indian proverb states: “Having a daughter is like watering your neighbors garden”.
As of today, with advanced technology of abortions, and ultra sounds to determine the sex of a child…it has become easy and efficient to end a pregnancy before birth.
The need that families have for boys is poignant, and when discovering that they’re soon to be baby will be a girl…abortions or can infanticide occurs. 21st century technology plus old-fashioned beliefs do not mix well together. There has been an abuse of this technology resulting in the infanticide and abortions of female girls.
Laws will not be as effective. In order to be successful there must be a cultural revolution of some sort to put females in a respected part of society, so that this infanticide of females no longer occurs.
- Williamson, Laila (1978). "Infanticide: an anthropological analysis". in Kohl, Marvin. Infanticide and the Value of Life. NY: Prometheus Books. pp. 61–75..
- Boswell, John Eastburn (1984). "Exposition and oblation: the abandonment of children and the ancient and medieval family". American Historical Review 89 (1): 10–33
- Hughes, Dennis D. (1991). Human Sacrifice in Ancient Greece. Routledge. pp. 187.
- Knapp, A. Bernard. Prehistoric and protohistoric Cyprus: identity, insularity, and connectivity . Oxford: Oxford Press, 2008.
- Naphtali, Lewis, ed (1985). "Papyrus Oxyrhynchus 744". Life in Egypt Under Roman Rule. Oxford: Oxford University Press. pp. 54..
- Radbill, Samuel X. (1974). "A history of child abuse and infanticide". in Steinmetz, Suzanne K. and Murray A. Straus. Violence in the Family. NY: Dodd, Mead; Co.. pp. 173–179.
- Boswell, John (1988). The Kindness of Strangers. NY: Vintage Books
- Robinson, J. Armitage (translator), ed (1920). "Didache". Barnabas, Hermar and the Didache. D.ii.2c. NY: The MacMillan Co.. pp. 112.
- Dorson, Richard (1968). Peasant Customs and Savage Myths: Selections from the British Folklorists. Chicago: University of Chicago Press. pp. 351
- Edited by Jane Dammen McAuliffe et al., Encyclopaedia of Qur'an 1st Edition., 5 vols. plus index., Leiden: Brill Publishers, 2001-2006, ISBN 90-04-14743-8
- Polo, Marco (1965). The Travels. Middlesex: Penguin Books. pp. 174.
- Yu-Lan, Fung (1952). A History of Chinese Philosophy. Princeton: Princeton University Press. pp. 327.
- ao, Esther S. Lee (1983). Chinese Women: Past and Present. Mesquite: Ide House. pp. 75.
- Vaux, Kenneth (1989). Birth Ethics. NY: Crossroad. pp. 12.