Challenge to the assumed rarity of heteropaternal superfecundation: findings from a case report

© 2019, © 2019 Australian Academy of Forensic Sciences. Heteropaternal superfecundation (HP) is the fertilization, within the same cycle, of simultaneously released ova by sperm from separate males. The twin offspring resulting from HP are genetically equivalent to half-siblings, sharing an average of 25% of their genetic complement, by descent. The frequency of such twins is unknown and assumed to be rare, but is likely to be underestimated. Reasons for underestimation include inadequate detection, absence of confirmation, links between illegitimate births and dizygotic twinning, modern reproductive technologies and public unawareness of such pairs. A recently identified case of heteropaternal female twins is illustrative in this regard. HP twins pose significant implications for paternity suits, organ donation and other forensic inquiries. Recognizing the importance of this special class of non-identical twins is further emphasized, given that their inclusion in modest size twin samples might spuriously inflate estimates of genetic influence underlying measured traits.