In some periods of Roman history it was traditional practice for a newborn to be brought to the pater familias, the family patriarch, who would then decide whether the child was to be kept and raised, or left to death by exposure. The Twelve Tables of Roman law obliged the pater familias to put to death a child that was visibly deformed. Although infanticide became a capital offense in Roman law in 374 CE, offenders were rarely if ever prosecuted. A practice described in Roman texts was to smear the breast with opium residue so that a nursing baby would die with no outward cause.
In some cases, infanticide may have been practiced to eliminate children with birth defects or circumstances of birth deemed unfavorable for religious reasons. The extent of such practices is often widely debated; for instance, academics argue whether infanticide of children with birth defects was a standard practice in ancient Greece, or limited to occasional incidents. It has also been alleged that twins were, in some societies, considered unlucky and thus exposed, though again the extent of such practices is debated.
Contemporary data suggests that modern infanticide is usually brought about by a combination of postpartum depression and a psychological unreadiness to raise children. It could also be exacerbated by schizophrenia. It is also attributed, in some cases, to the desire of unwed, underaged parents to conceal their sexual relations and/or avoid the responsibility of childrearing.