Although there are a range of reasons, the most recent study of experiences of women who adopt suggests they are most likely to be 40–44 years of age, to be currently married, to have impaired fertility, and to be childless.Unrelated adoptions may occur through the following mechanisms:

Private domestic adoptions: under this arrangement, charities and for-profit organizations act as intermediaries, bringing together prospective adoptive parents with 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. 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, about 51,000 or 40% were through the foster care system. International adoption: this involves the placing of a child for adoption outside that childs country of birth. This can occur through public or private agencies. In some countries, such as Sweden, these adoptions account for the majority of cases (see above table).
Officials of the BFA noted that, although the asylum promoted otherwise, adoptive parents did not distinguish between indenture and adoption: "We believe," the asylum officials said, "that often, when children of a younger age are taken to be adopted, the adoption is only another name for service." Modern period
Adopting to create a familyThe next stage of adoptions evolution fell to the emerging nation of the United States. Rapid immigration and the American Civil War resulted in unprecedented overcrowding of orphanages and foundling homes in the mid-nineteenth century. Charles Loring Brace, a Protestant minister, became appalled by the legions of homeless waifs roaming the streets of New York City. Brace considered the abandoned youth, particularly Catholics, to be the most dangerous element challenging the citys order. 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 nations rural regions. The children were generally indentured, rather than adopted, to families who took them in. As in times past, some children were raised as members of the family while others were used as farm laborers and household servants. 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.