Infant adoption during Antiquity appears rare.[4][7] Abandoned children were often picked up for slavery[8] and composed a significant percentage of the Empire's slave supply.[9][10] Roman legal records indicate that foundlings were occasionally taken in by families and raised as a son or daughter. Although not normally adopted under Roman Law, the children, called alumni, were reared in an arrangement similar to guardianship, being considered the property of the father who abandoned them.[11]
Ad hoc studies, performed in the U.S., however, suggest that between 10 and 25 percent of adoptions through the child welfare system (e.g., excluding babies adopted from other countries or stepparents adopting their stepchildren) disrupt before they are legally finalized and from 1 to 10 percent are dissolved after legal finalization. The wide range of values reflects the paucity of information on the subject and demographic factors such as age; it is known that teenagers are more prone to having their adoptions disrupted than young children.[91]

As the idea of institutional care gained acceptance, formal rules appeared about how to place children into families: boys could become apprenticed to an artisan and girls might be married off under the institution's authority.[19] Institutions informally adopted out children as well, a mechanism treated as a way to obtain cheap labor, demonstrated by the fact that when the adopted died, their bodies were returned by the family to the institution for burial.[20]
Common law adoption: this is an adoption which has not been recognized beforehand by the courts, but where a parent, without resorting to any formal legal process, leaves his or her children with a friend or relative for an extended period of time.[88][89] At the end of a designated term of (voluntary) co-habitation, as witnessed by the public, the adoption is then considered binding, in some courts of law, even though not initially sanctioned by the court. The particular terms of a common-law adoption are defined by each legal jurisdiction. For example, the US state of California recognizes common law relationships after co-habitation of 2 years. The practice is called "private fostering" in Britain.[90]

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.[166]
Family preservation: As concerns over illegitimacy began to decline in the early 1970s, social-welfare agencies began to emphasize that, if possible, mothers and children should be kept together.[156] In the U.S., this was clearly illustrated by the shift in policy of the New York Foundling Home, an adoption-institution that is among the country's oldest and one that had pioneered sealed records. It established three new principles including "to prevent placements of children...," reflecting the belief that children would be better served by staying with their biological families, a striking shift in policy that remains in force today.[157]

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.[167]

As a reaction against the bans and hurdles affecting international adoption, scholars Elizabeth Bartholet and Paulo Barrozo claim that every child has a right to a family as a matter of basic human rights.[citation needed] This claim devalues heritage or "cultural" claims and emphasizes the child's existence as a human being rather than a "property" of specific nations or, for example, abusive caregivers.

Foster care adoption: this is a type of domestic adoption where a child is initially placed in public care. Many times the foster parents take on the adoption when the children become legally free. Its importance as an avenue for adoption varies by country. Of the 127,500 adoptions in the U.S. in 2000[83] about 51,000 or 40% were through the foster care system.[84]

Adoption is the legal process through which a child joins a family different from his or her birth parents. Adoption is a permanent, lifelong commitment to a child. In CPS cases, adoption becomes an option if CPS and the child's birth parents cannot resolve issues that made it unsafe for the child to live at home. Then, CPS may ask the court to end the parents' rights to the child and place the child with another family permanently. A child can also become legally free for adoption if both birth parents agree to give up their parental rights.

In the 1970s, as adoption search and support organizations developed, there were challenges to the language in common use at the time. As books like Adoption Triangle by Sorosky, Pannor and Baran were published, and support groups formed like CUB (Concerned United Birthparents), a major shift from "natural parent" to "birthparent"[182][183] occurred. Along with the change in times and social attitudes came additional examination of the language used in adoption.