There is limited research on the consequences of adoption for the original parents, and the findings have been mixed. One study found that those who released their babies for adoption were less comfortable with their decision than those who kept their babies. However, levels of comfort over both groups were high, and those who released their child were similar to those who kept their child in ratings of life satisfaction, relationship satisfaction, and positive future outlook for schooling, employment, finances, and marriage.[121] Subsequent research found that adolescent mothers who chose to release their babies for adoption were more likely to experience feelings of sorrow and regret over their decision than those who kept their babies. However, these feelings decreased significantly from one year after birth to the end of the second year.[122]

Similar mechanisms appear to be at work in the physical development of adoptees. Danish and American researchers conducting studies on the genetic contribution to body mass index found correlations between an adoptee's weight class and his biological parents' BMI while finding no relationship with the adoptive family environment. Moreover, about one-half of inter-individual differences were due to individual non-shared influences.[115][116]

Evidence about the development of adoptees can be supported in newer studies. It can be said that adoptees, in some respect, tend to develop differently from the general population. This can be seen in many aspects of life, but usually can be found as a greater risk around the time of adolescence. For example, it has been found that many adoptees experience difficulty in establishing a sense of identity.[126]
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.[114]
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.
Private domestic adoptions: under this arrangement, charities and for-profit organizations act as intermediaries, bringing together prospective adoptive parents and families who want to place a child, all parties being residents of the same country. Alternatively, prospective adoptive parents sometimes avoid intermediaries and connect with women directly, often with a written contract; this is not permitted in some jurisdictions. Private domestic adoption accounts for a significant portion of all adoptions; in the United States, for example, nearly 45% of adoptions are estimated to have been arranged privately.[83]
Open records: Movements to unseal adoption records for adopted citizens proliferated along with increased acceptance of illegitimacy. In the United States, Jean Paton founded Orphan Voyage in 1954, and Florence Fisher founded the Adoptees' Liberty Movement Association (ALMA) in 1971, calling sealed records "an affront to human dignity.".[158] While in 1975, Emma May Vilardi created the first mutual-consent registry, the International Soundex Reunion Registry (ISRR), allowing those separated by adoption to locate one another.[159] and Lee Campbell and other birthmothers established CUB (Concerned United Birthparents). Similar ideas were taking hold globally with grass-roots organizations like Parent Finders in Canada and Jigsaw in Australia. In 1975, England and Wales opened records on moral grounds.[160]
Psychologists' findings regarding the importance of early mother-infant bonding created some concern about whether parents who adopt older infants or toddlers after birth have missed some crucial period for the child's development. However, research on The Mental and Social Life of Babies suggested that the "parent-infant system," rather than a bond between biologically related individuals, is an evolved fit between innate behavior patterns of all human infants and equally evolved responses of human adults to those infant behaviors. Thus nature "ensures some initial flexibility with respect to the particular adults who take on the parental role."[96]
Identity is defined both by what one is and what one is not. Adoptees born into one family lose an identity and then borrow one from the adopting family. The formation of identity is a complicated process and there are many factors that affect its outcome. From a perspective of looking at issues in adoption circumstances, the people involved and affected by adoption (the biological parent, the adoptive parent and the adoptee) can be known as the "triad members and state". Adoption may threaten triad members' sense of identity. Triad members often express feelings related to confused identity and identity crises because of differences between the triad relationships. Adoption, for some, precludes a complete or integrated sense of self. Triad members may experience themselves as incomplete, deficient, or unfinished. They state that they lack feelings of well-being, integration, or solidity associated with a fully developed identity.[129]
Embryo adoption: based on the donation of embryos remaining after one couple's in vitro fertilization treatments have been completed; embryos are given to another individual or couple, followed by the placement of those embryos into the recipient woman's uterus, to facilitate pregnancy and childbirth. In the United States, embryo adoption is governed by property law rather than by the court systems, in contrast to traditional adoption.
His solution was outlined in The Best Method of Disposing of Our Pauper and Vagrant Children (1859) which started the Orphan Train movement. The orphan trains eventually shipped an estimated 200,000 children from the urban centers of the East to the nation's rural regions.[28] The children were generally indentured, rather than adopted, to families who took them in.[29] As in times past, some children were raised as members of the family while others were used as farm laborers and household servants.[30] The sheer size of the displacement—the largest migration of children in history—and the degree of exploitation that occurred, gave rise to new agencies and a series of laws that promoted adoption arrangements rather than indenture. The hallmark of the period is Minnesota's adoption law of 1917 which mandated investigation of all placements and limited record access to those involved in the adoption.[31][32]