Zygosity diagnosis in young twins by parental report

Twin Res. 2000 Sep;3(3):134-41. doi: 10.1375/136905200320565409.


This study reports on zygosity determination in twins of childhood age. Parents responded to questionnaire items dealing with twin similarity in physical characteristics and frequency of mistaking one twin for another by parents, relatives and strangers. The accuracy of zygosity diagnosis was evaluated across twins aged 6, 8, and 10 and across parents. In addition, it was examined whether the use of multiple raters and the use of longitudinal data lead to an improvement of zygosity assignment. Complete data on zygosity questions and on genetic markers or blood profiles were available for 618 twin pairs at the age of 6 years. The method used was predictive discriminant analyses. Agreement between zygosity assigned by the replies to the questions and zygosity determined by DNA markers/blood typing was around 93%. The accuracy of assignment remained constant across age and parents. Analyses of data provided by both parents and collected over multiple ages did not result in better prediction of zygosity. Details on the discriminant function are provided.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Blood Group Antigens / genetics
  • Chi-Square Distribution
  • Child
  • Discriminant Analysis
  • Fathers
  • Female
  • Forecasting
  • Genetic Markers / genetics
  • Humans
  • Interpersonal Relations
  • Longitudinal Studies
  • Male
  • Mothers
  • Netherlands
  • Parent-Child Relations
  • Parents*
  • Surveys and Questionnaires
  • Twins, Dizygotic* / genetics
  • Twins, Monozygotic* / genetics


  • Blood Group Antigens
  • Genetic Markers