A closed adoption is one in which there is no exchange of information between adopting and placing parents and, after the adoption, between adoptive and birth parents.
Closed adoptions were the norm during the first seven decades of the 20th century. In the earlier part of the 20th century, closed adoptions offered privacy to both placing and adopting parents, in a time when reasons for placing and reasons for adopting were rarely discussed in public. During the 40s, 50s, and 60s, prevailing opinions of social work professionals were that any exchange of information could be potentially damaging to the adoptive parent-adopted child relationship, and although it wasn't often verbalized, there was an underlying belief that birth parents might try to find the child and intrude in or disrupt the adoptive family life.
Toward the end of the 20th century, several factors contributed to the drop in closed adoptions and the tendency to open up the channels of communication between placing and adopting - and birth and adoptive - parents.