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Is recreational running associated with earlier delivery and lower birth weight in women who continue to run during pregnancy? An international retrospective cohort study of running habits of 1293 female runners during pregnancy
  1. Katy Kuhrt,
  2. Mark Harmon,
  3. Natasha L Hezelgrave,
  4. Paul T Seed,
  5. Andrew H Shennan
  1. Division of Women’s Health, King’s College London, St Thomas’ Hospital, London, UK
  1. Correspondence to Dr Andrew H Shennan; andrew.shennan{at}


Background Increasingly, women of reproductive age participate in recreational running, but its impact on pregnancy outcome is unknown. We investigated whether running affects gestational age at delivery and birth weight as indicators of cervical integrity and placental function, respectively.

Methods 1293 female participants were recruited from parkrun, which organises weekly runs involving 1.25 million runners across 450 parks worldwide. Those under 16 or unable to provide outcome data were excluded. Women were categorised according to whether they continued to run during pregnancy or not. Those who continued were further stratified dependent on average weekly kilometres, and which trimester they ran until. Retrospectively collected primary outcomes were gestational age at delivery and birthweight centile. Other outcomes included assisted vaginal delivery rate and prematurity at clinically important gestations.

Results There was no significant difference in gestational age at delivery: 279.0 vs 279.6 days (mean difference 0.6 days, CI −1.3 to 2.4 days; P=0.55) or birthweight centile: 46.9%vs 44.9% (mean difference 2.0%, CI −1.3% to −5.3%; P=0.22) in women who stopped running and those who continued, respectively. Assisted vaginal delivery rate was increased in women who ran: 195/714 (27%) vs 128/579 (22%) (OR 1.32; CI 1.02 to 1.71; P=0.03).

Conclusion Continuing to run during pregnancy does not appear to affect gestational age or birthweight centile, regardless of mean weekly distance or stage of pregnancy. Assisted vaginal delivery rates were higher in women who ran, possibly due to increased pelvic floor muscle tone. Randomised prospective analysis is necessary to further explore these findings.

  • running
  • pregnancy
  • exercise

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  • Contributors KK analysed the results and wrote the paper. MH designed the survey, distributed it among study participants and reviewed the draft paper. NLH was involved in the initiation of the idea for the study, analysis of results and writing of the paper. PTS designed and conducted statistical analysis and revised the draft paper. AHS devised the idea for the study and coordinated planning, analysis, reporting of results and was involved in writing the paper. He is guarantor.

  • Competing interests None declared.

  • Ethics approval The Health Research Authority decision making tool advised that NHS Research Ethics committee approval was not needed. Guy’s and St Thomas’ NHS Foundation Trust Research and Development Department confirmed that trust approval was not required for this work.

  • Data sharing statement All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis.