The concept of unintended pregnancy has been used by demographers, public health and social science researchers to investigate maternal and, in the case of live birth, child outcomes. Recent data show that an estimated 34% in Western Europe to 54% in Eastern Europe of pregnancies are unintended, despite 50 years of available effective contraception. In fact, contraception prevalence has been found to have no effect on excess fertility, while the challenge of reducing fertility has translated into one of reducing fertility desire rather than reducing unwanted fertility. Unwanted childbearing-- the mismatch between actual and desired fertility-- is extensive in high-fertility societies. Anthropological studies and ethnographies among traditional societies provide an in-depth insight into the socioeconomic and cultural circumstances relating to why some children are deemed undesirable, how and why unwanted children are treated by their mothers and caregivers, and the physical and mental consequences of being an unwanted child. Disinvesting in unwanted children has occurred in our species since its origin, and occurs in many cultures and populations. Throughout history and across cultures, mothers have chosen various ways to disinvest in unwanted children, e.g. infanticide, abandonment, giving the child to kin to raise, and leaving the child at foundling hospitals or orphanages. Maternal decision-making is dependent on specific demographic, ecological, and cultural contexts, where maternal options are additionally restricted by fitness trade-offs.