These practices have become significant social and political issues in recent years, and in many cases the policies have changed. The United States, for example, now has the 1978 Indian Child Welfare Act, which allows the tribe and family of a Native American child to be involved in adoption decisions, with preference being given to adoption within the child's tribe.
Concerning developmental milestones, studies from the Colorado Adoption Project examined genetic influences on adoptee maturation, concluding that cognitive abilities of adoptees reflect those of their adoptive parents in early childhood but show little similarity by adolescence, resembling instead those of their biological parents and to the same extent as peers in non-adoptive families.
The period 1945 to 1974, the baby scoop era, saw rapid growth and acceptance of adoption as a means to build a family. Illegitimate births rose three-fold after World War II, as sexual mores changed. Simultaneously, the scientific community began to stress the dominance of nurture over genetics, chipping away at eugenic stigmas. In this environment, adoption became the obvious solution for both unwed people and infertile couples.
Nevertheless, some indication of the level of search interest by adoptees can be gleaned from the case of England and Wales which opened adoptees' birth records in 1975. The UK Office for National Statistics has projected that 33% of all adoptees would eventually request a copy of their original birth records, exceeding original forecasts made in 1975 when it was believed that only a small fraction of the adoptee population would request their records. The projection is known to underestimate the true search rate, however, since many adoptees of the era get their birth records by other means.
In Spain under Francisco Franco’s 1939–75 dictatorship the newborns of some left-wing opponents of the regime, or unmarried or poor couples, were removed from their mothers and adopted. New mothers were frequently told their babies had died suddenly after birth and the hospital had taken care of their burials, when in fact they were given or sold to another family. It is believed that up to 300,000 babies were involved. These system – which allegedly involved doctors, nurses, nuns and priests – outlived Franco’s death in 1975 and carried on as an illegal baby trafficking network until 1987 when a new law regulating adoption was introduced.
Adoption practices have changed significantly over the course of the 20th century, with each new movement labeled, in some way, as reform. Beginning in the 1970s, efforts to improve adoption became associated with opening records and encouraging family preservation. These ideas arose from suggestions that the secrecy inherent in modern adoption may influence the process of forming an identity, create confusion regarding genealogy, and provide little in the way of medical history.
The research literature states adoptees give four reasons for desiring reunion: 1) they wish for a more complete genealogy, 2) they are curious about events leading to their conception, birth, and relinquishment, 3) they hope to pass on information to their children, and 4) they have a need for a detailed biological background, including medical information. It is speculated by adoption researchers, however, that the reasons given are incomplete: although such information could be communicated by a third-party, interviews with adoptees, who sought reunion, found they expressed a need to actually meet biological relations.