Background: This study presents findings from a large sample of donor offspring who are aware of the nature of their conception. Importantly, this is one of the first studies to compare the views of offspring told of their origins during childhood to those who found out during adulthood.

Methods: Online questionnaires were completed anonymously by donor offspring who were members of the Donor Sibling Registry, a US-based worldwide registry that helps donor-conceived individuals search for and contact their donor and donor siblings (i.e. half-siblings). Data were obtained on offspring's feelings about being donor conceived and their feelings towards their parents.

Results: Offspring of single mothers and lesbian couples learnt of their donor origins earlier than offspring of heterosexual couples. Those told later in life reported more negative feelings regarding their donor conception than those told earlier. Offspring's feelings towards their parents were less clear, with some of those told later reporting more positive feelings and others reporting more negative feelings. Offspring from heterosexual-couple families were more likely to feel angry at being lied to by their mothers than by their fathers. The most common feeling towards fathers was 'sympathetic'.

Conclusions: Age of disclosure is important in determining donor offspring's feelings about their donor conception. It appears it is less detrimental for children to be told about their donor conception at an early age.