Genetic and environmental factors affecting birth size variation: A pooled individual-based analysis of secular trends and global geographical differences using 26 twin cohorts

Research output: Contribution to journalArticle


Background: The genetic architecture of birth size may differ geographically and over time. We examined differences in the genetic and environmental contributions to birthweight, length and ponderal index (PI) across geographical-cultural regions (Europe, North America and Australia, and East Asia) and across birth cohorts, and how gestational age modifies these effects. Methods: Data from 26 twin cohorts in 16 countries including 57 613 monozygotic and dizygotic twin pairs were pooled. Genetic and environmental variations of birth size were estimated using genetic structural equation modelling. Results: The variance of birthweight and length was predominantly explained by shared environmental factors, whereas the variance of PI was explained both by shared and unique environmental factors. Genetic variance contributing to birth size was small. Adjusting for gestational age decreased the proportions of shared environmental variance and increased the propositions of unique environmental variance. Genetic variance was similar in the geographical-cultural regions, but shared environmental variance was smaller in East Asia than in Europe and North America and Australia. The total variance and shared environmental variance of birth length and PI were greater from the birth cohort 1990-99 onwards compared with the birth cohorts from 1970-79 to 1980-89. Conclusions: The contribution of genetic factors to birth size is smaller than that of shared environmental factors, which is partly explained by gestational age. Shared environmental variances of birth length and PI were greater in the latest birth cohorts and differed also across geographical-cultural regions. Shared environmental factors are important when explaining differences in the variation of birth size globally and over time.


  • Yoshie Yokoyama
  • Aline Jelenkovic
  • Yoon Mi Hur
  • Reijo Sund
  • Corrado Fagnani
  • Maria A. Stazi
  • Sonia Brescianini
  • Fuling Ji
  • Feng Ning
  • Zengchang Pang
  • Ariel Knafo-Noam
  • David Mankuta
  • Lior Abramson
  • Esther Rebato
  • John L Hopper
  • Tessa L. Cutler
  • Kimberly J. Saudino
  • Tracy L. Nelson
  • Keith E. Whitfield
  • Robin P. Corley
  • And 40 others
  • Brooke M. Huibregtse
  • Catherine A. Derom
  • Robert F. Vlietinck
  • Ruth J.F. Loos
  • Clare H. Llewellyn
  • Abigail Fisher
  • Morten Bjerregaard-Andersen
  • Henning Beck-Nielsen
  • Morten Sodemann
  • Robert F. Krueger
  • Matt McGue
  • Shandell Pahlen
  • Meike Bartels
  • Catharina E.M. Van Beijsterveldt
  • Gonneke Willemsen
  • Jennifer R. Harris
  • Ingunn Brandt
  • Thomas S. Nilsen
  • Jeffrey M. Craig
  • Richard Saffery
  • Lise Dubois
  • Michel Boivin
  • Mara Brendgen
  • Ginette Dionne
  • Frank Vitaro
  • Claire M.A. Haworth
  • Robert Plomin
  • Gombojav Bayasgalan
  • Danshiitsoodol Narandalai
  • Finn Rasmussen
  • Per Tynelius
  • Adam D. Tarnoki
  • David L. Tarnoki
  • Syuichi Ooki
  • Richard J. Rose
  • Kirsi H. Pietiläinen
  • Thorkild I.A. Sørensen
  • Dorret I. Boomsma
  • Jaakko Kaprio
  • Karri Silventoinen
External organisations
  • Osaka City University
  • University of Helsinki
  • University of the Basque Country
  • Mokpo National University
  • University of Eastern Finland
  • Istituto Superiore di Sanità
  • Hebrew University of Jerusalem
  • Hebrew University-Hadassah Medical School
  • University of Melbourne
  • Seoul National University
  • Boston University
  • Colorado State University
  • Duke University
  • University of Colorado
  • University Hospitals Leuven
  • Ghent University Hospital
  • Icahn School of Medicine at Mount Sinai
  • University College London
  • Bandim Health Project, Indepth Network
  • Danish Serum Institute, Copenhagen
  • Odense University Hospital
  • University of Minnesota system
  • Norwegian Institute of Public Health
  • Royal Children's Hospital, Melbourne
  • University of Ottawa
  • Laval University
  • Tomsk State University
  • University of Montreal, Canada
  • University of Bristol
  • King's College London
  • Healthy Twin Association of Mongolia
  • Hiroshima University
  • Karolinska Institutet
  • Semmelweis University
  • Hungarian Twin Registry
  • Indiana University
  • Helsinki University Central Hospital
  • University of Copenhagen
  • Chinese University of Hong Kong
  • Institute for Molecular Medicine Finland (FIMM)
  • Osaka University
  • Chinese Center for Disease Control and Prevention
  • University of Amsterdam
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Public Health, Global Health, Social Medicine and Epidemiology


  • Birth length, Birthweight, Genetics, Ponderal index, Pooled studies, Twins
Original languageEnglish
Pages (from-to)1195-1206
Number of pages12
JournalInternational Journal of Epidemiology
Issue number4
Publication statusPublished - 2018 Aug 1
Publication categoryResearch