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Danish premature birth rates during the COVID-19 lockdown
  1. Gitte Hedermann1,
  2. Paula Louise Hedley1,
  3. Marie Bækvad-Hansen1,2,
  4. Henrik Hjalgrim3,4,
  5. Klaus Rostgaard3,
  6. Porntiva Poorisrisak5,
  7. Morten Breindahl5,
  8. Mads Melbye3,6,7,
  9. David M Hougaard1,2,
  10. Michael Christiansen1,8,
  11. Ulrik Lausten-Thomsen5
  1. 1 Department for Congenital Disorders, Danish National Biobank and Biomarkers, Statens Serum Institut, Copenhagen, Denmark
  2. 2 Danish Center for Neonatal Screening, Statens Serum Institut, Copenhagen, Denmark
  3. 3 Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark
  4. 4 Department of Haematology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
  5. 5 Department of Neonatology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
  6. 6 Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
  7. 7 Department of Medicine, Stanford University School of Medicine, Stanford, CA, US
  8. 8 Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
  1. Correspondence to Dr Michael Christiansen, Statens Serum Institut, Copenhagen, Denmark; mic{at}; Dr Ulrik Lausten-Thomsen, Rigshospitalet, Copenhagen, Denmark; ulrik.lausten-thomsen{at}


To explore the impact of COVID-19 lockdown on premature birth rates in Denmark, a nationwide register-based prevalence proportion study was conducted on all 31 180 live singleton infants born in Denmark between 12 March and 14 April during 2015–2020.

The distribution of gestational ages (GAs) was significantly different (p=0.004) during the lockdown period compared with the previous 5 years and was driven by a significantly lower rate of extremely premature children during the lockdown compared with the corresponding mean rate for the same dates in the previous years (OR 0.09, 95% CI 0.01 to 0.40, p<0.001). No significant difference between the lockdown and previous years was found for other GA categories.

The reasons for this decrease are unclear. However, the lockdown has provided a unique opportunity to examine possible factors related to prematurity. Identification of possible causal mechanisms might stimulate changes in clinical practice.

  • epidemiology
  • neonatology

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  • GH and PLH are joint first authors.

  • MC and UL-T are joint senior authors.

  • GH and PLH contributed equally.

  • MC and UL-T contributed equally.

  • Correction notice This paper has been amended since it was published online. The provenance and peer review of this article has been changed to externally peer reviewed.

  • Contributors GH, PLH, DMH, MC and UL-T designed the study. GH and MB-H collected the data. PLH, KR, MC and UL-T performed statistical analyses. GH, PLH, MC and UL-T co-wrote first draft. All authors contributed to the interpretation of the data and critically revised the manuscript, had full access to tables and figures in the study, and take responsibility for the integrity of the data.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests MB has a patent (NeoHelp) with royalties paid.

  • Patient consent for publication Not required.

  • Ethics approval Statens Serum Institut has approval from the Danish Data Protection Agency (DPA) to conduct register-based studies, and the current study was approved by the DPA officer (approval no: 20/04753) at Statens Serum Institut. Studies based solely on register data do not require further ethics committee approval as per Danish laws and regulations.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. The process of accessing data from the Danish National Biobanks is detailed online ( No additional data are available.

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