title: Why Accurate Knowledge of Zygosity is Important to Twins.
abstract: All same-sex dizygotic (DZ) twins and approximately one-third of monozygotic (MZ) twin pairs have separate placentas, making it impossible to use the number of placentas to determine zygosity. Zygosity determination is further complicated because incorrect assumptions are often made, such as that only DZ pairs have two placentas and that all MZ pairs are phenotypically identical. These assumptions, by twins, their families and health professionals, along with the lack of universal zygosity testing for same-sex twins, has led to confusion within the twin community, yet little research has been conducted with twins about their understanding and assumptions about zygosity. We aimed to explore and quantify understanding and assumptions about zygosity using twins attending an Australian twin festival. We recruited 91 twin pairs younger than 18 years of age and their parents, and 30 adult twin pairs who were all uncertain of their zygosity, to complete one pen and paper questionnaire and one online questionnaire about their assumed zygosity, reasons for their assumptions and the importance of accurate zygosity knowledge. Responses were compared with their true zygosity measured using a genetic test. We found a substantial proportion of parents and twins had been misinformed by their own parents or medical professionals, and that knowledge of their true zygosity status provided peace of mind and positive emotional responses. For these reasons we propose universal zygosity testing of same-sex twins as early in life as possible and an increase in education of medical professionals, twins and families of twins about zygosity issues.
authors: Australian Twin Registry,Melbourne School of Population and Global Health,The University of Melbourne,Melbourne,Victoria,Australia.
authors: Tessa L
authors: TL
authors: Cutler
authors: Australian Twin Registry,Melbourne School of Population and Global Health,The University of Melbourne,Melbourne,Victoria,Australia.
authors: Kate
authors: K
authors: Murphy
authors: Australian Twin Registry,Melbourne School of Population and Global Health,The University of Melbourne,Melbourne,Victoria,Australia.
authors: John L
authors: JL
authors: Hopper
authors: Centre for Health Equity,Melbourne School of Population and Global Health,The University of Melbourne,Melbourne,Victoria,Australia.
authors: Louise A
authors: LA
authors: Keogh
authors: Murdoch Childrens Research Institute and University of Melbourne Department of Paediatrics,Royal Children's Hospital,Melbourne,Victoria,Australia.
authors: Yun
authors: Y
authors: Dai
authors: Australian Twin Registry,Melbourne School of Population and Global Health,The University of Melbourne,Melbourne,Victoria,Australia.
authors: Jeffrey M
authors: JM
authors: Craig
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001294:Attitude to Health; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004247:DNA / Q000235:genetics; D030881:Disclosure; D004644:Emotions; D005106:Exploratory Behavior; D005260:Female; D005838:Genotype; D006806:Human Rights; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010290:Parents / Q000523:psychology; D033283:Patient Access to Records; D012649:Self Concept; D012801:Sibling Relations; D014429:Twins, Dizygotic / Q000235:genetics / Q000523:psychology*; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology*; D014739:Victoria; D055815:Young Adult
chemical_list: D004247:DNA
keywords: DNA; questionnaire; twin study; twins; validation study; zygosity; zygosity determination