The seventh phase of this longitudinal study investigated whether children born through third-party assisted reproduction experienced psychological problems, or difficulties in their relationship with their mothers, in early adulthood. The impact of disclosure of their biological origins, and quality of mother-child relationships from age 3 onward, were also examined. Sixty-five assisted reproduction families, including 22 surrogacy families, 17 egg donation families, and 26 sperm donation families, were compared with 52 unassisted conception families when the children were aged 20. Less than half of the mothers had completed tertiary education and less than 5% were from ethnic minority backgrounds. Standardized interviews and questionnaires were administered to mothers and young adults. There were no differences between assisted reproduction and unassisted conception families in mothers' or young adults' psychological well-being, or the quality of family relationships. However, within the gamete donation families, egg donation mothers reported less positive family relationships than sperm donation mothers, and young adults conceived by sperm donation reported poorer family communication than those conceived by egg donation. Young adults who learned about their biological origins before age 7 had less negative relationships with their mothers, and their mothers showed lower levels of anxiety and depression. Associations between parenting and child adjustment did not differ between assisted and unassisted reproduction families from ages 3 to 20. The findings suggest that the absence of a biological connection between children and their parents in assisted reproduction families does not interfere with the development of positive mother-child relationships or psychological adjustment in adulthood.