Prior to the development of modern birth control, many societies practiced infanticide as a means of family planning. Up until modern times, most cultures at the least tolerated the practice if not fully endorsed it. This month’s Journal of Archaeological Science has one of the most thorough, modern investigations into the Roman practice. Historians have long suspected that the Romans practiced infanticide, it is cursorily referenced in many ancient texts, and research studies have seemed to confirm the practice.
Research at the Hambelden Villa in England has uncovered at least 97 infant burials. Now, as infant remains rarely display cause of death (due to the nature of their development and skeletons), traditional methods of investigation are not always reliable. A survey of infant burials from natural causes would anticipate a wider range of age and development (from newborn to one year). Evidence of infanticide provides a more uniform age of death at the newborn stage.
You can read more about the article and their findings in this article by Discovery.