Parental Age and Birth Defects: A Sibling Study

Hans Hvide* (Corresponding Author), Julian Johnsen, Kjell G. Salvanes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)
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Higher parental age at childbearing has generated much attention as a potential risk factor for birth disorders; however, previous research findings are mixed. Existing studies have exploited variation in parental age across families, which is problematic because families differ not only in parental age but also in genetic and environmental factors. To isolate the effects of parental age, holding many genetic and environmental factors constant, we exploit the variation in parental age within families and compare outcomes for full siblings. The study data were retrieved from the Medical Birth Registry of Norway, which covers the entire population of births in Norway over an extended period (totaling 1.2 million births). Using variation in parental age when siblings were born, we find large and convex effects of increased parental age on the increased risk of birth disorders. To facilitate comparison with the existing literature, we also estimate the effects of parental age using variation in parental age across families and find that the effects are substantially weaker. We conclude that the existing literature may have underestimated the negative effects of parental aging on adverse offspring outcomes.
Original languageEnglish
Pages (from-to)849-860
Number of pages12
JournalEuropean Journal of Epidemiology
Issue number8
Early online date24 Mar 2021
Publication statusPublished - Aug 2021

Bibliographical note

Open access funding provided by University of Bergen (incl Haukeland University Hospital).


  • birth disorder
  • congenital anomalies
  • parental aging
  • stillbirth


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