Preterm birth after the introduction of COVID-19 mitigation measures in Norway, Sweden, and Denmark: a registry-based difference-in-differences study

Research output: Contribution to journalJournal articleResearchpeer-review


  • Preterm

    Final published version, 2.25 MB, PDF document

  • Laura L. Oakley
  • Anne K. Ortqvist
  • Jonas Kinge
  • Anne Vinkel Hansen
  • Tanja Gram Petersen
  • Jonas Soderling
  • Kjetil E. Telle
  • Maria C. Magnus
  • Laust Hvas Mortensen
  • Nybo Andersen, Anne-Marie
  • Olof Stephansson
  • Siri E. Haberg

BACKGROUND: Although some studies have reported a decrease in preterm birth following the start of the COVID-19 pandemic, the findings are inconsistent.

OBJECTIVE: This study aimed to compare the incidences of preterm birth before and after the introduction of COVID-19 mitigation measures in Scandinavian countries using robust population-based registry data.

STUDY DESIGN: This was a registry-based difference-in-differences study using births from January 2014 through December 2020 in Norway, Sweden, and Denmark. The changes in the preterm birth (

RESULTS: A total of 1,519,521 births were included in this study. During the study period, 5.6% of the births were preterm in Norway and Sweden, and 5.7% were preterm in Denmark. There was a seasonal variation in the incidence of preterm birth, with the highest incidence during winter. In all the 3 countries, there was a slight overall decline in preterm births from 2014 to 2020. There was no consistent evidence of a change in the preterm birth rates following the introduction of COVID-19 mitigation measures, with difference-in-differences estimates ranging from 3.7 per 1000 births (95% confidence interval, -3.8 to 11.1) for the first 2 weeks after March 12, 2020, to -1.8 per 1000 births (95% confidence interval, -4.6 to 1.1) in the 16 weeks after March 12, 2020. Similarly, there was no evidence of an impact on medically indicated preterm birth, spontaneous preterm birth, or very preterm birth.

CONCLUSION: Using high-quality national data on births in 3 Scandinavian countries, each of which implemented different approaches to address the pandemic, there was no evidence of a decline in preterm births following the introduction of COVID-19 mitigation measures.

Original languageEnglish
Article numberARTN 550.e1-22
JournalAmerican Journal of Obstetrics and Gynecology
Issue number4
Number of pages22
Publication statusPublished - 2022

    Research areas

  • COVID-19, pregnancy outcomes, preterm birth, retrospective, Scandinavia, OUTCOMES, QUALITY, SYSTEM, IMPACT, POLICY, RATES

ID: 313862406