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Risk of recurrent spontaneous preterm birth: a systematic review and meta-analysis
  1. Courtney Phillips1,
  2. Zain Velji2,
  3. Ciara Hanly3,
  4. Amy Metcalfe4,5
  1. 1 Cumming School of Medicine, University of Calgary, Calgary, Canada
  2. 2 Faculty of Nursing, University of Calgary, Calgary, Canada
  3. 3 School of Kinesiology, University of British Columbia, Vancouver, Canada
  4. 4 Department of Obstetrics and Gynecology, University of Calgary, Calgary, Canada
  5. 5 Department of Community Health Sciences, University of Calgary, Calgary, Canada
  1. Correspondence to Dr Amy Metcalfe; amy.metcalfe{at}


Objective To determine the risk of recurrent spontaneous preterm birth (sPTB) following sPTB in singleton pregnancies.

Design Systematic review and meta-analysis using random effects models.

Data sources An electronic literature search was conducted in OVID Medline (1948–2017), Embase (1980–2017) and (completed studies effective 2017), supplemented by hand-searching bibliographies of included studies, to find all studies with original data concerning recurrent sPTB.

Study eligibility criteria Studies had to include women with at least one spontaneous preterm singleton live birth (<37 weeks) and at least one subsequent pregnancy resulting in a singleton live birth. The Newcastle-Ottawa Scale was used to assess study quality.

Results Overall, 32 articles involving 55 197 women, met all inclusion criteria. Generally studies were well conducted and had a low risk of bias. The absolute risk of recurrent sPTB at <37 weeks’ gestation was 30% (95% CI 27% to 34%). The risk of recurrence due to preterm premature rupture of membranes (PPROM) at <37 weeks gestation was 7% (95% CI 6% to 9%), while the risk of recurrence due to preterm labour (PTL) at <37 weeks gestation was 23% (95% CI 13% to 33%).

Conclusions The risk of recurrent sPTB is high and is influenced by the underlying clinical pathway leading to the birth. This information is important for clinicians when discussing the recurrence risk of sPTB with their patients.

  • preterm birth
  • preterm labor
  • preterm premature rupture of membranes
  • recurrence
  • systematic review

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  • Contributors All authors made a substantial contribution to this study. CP, ZV and CH conducted the systematic review. CP drafted the manuscript. AM designed the study and conducted the meta-analysis. All authors critically reviewed the manuscript, interpreted the findings, and approved the final version. All authors had full access to all of the data in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. As the senior author AM affirms that the manuscript is an honest, accurate, and transparent account of the study being reported, that no important aspects of the study have been omitted, and that any discrepancies from the study as planned have been explained.

  • Funding This study was funded by the Alberta Children’s Hospital Research Institute. Amy Metcalfe is supported by a New Investigator Award from the Canadian Institutes of Health Research. The funder had no role in study design, execution, or publication decisions.

  • Competing interests None declared.

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

  • Data sharing statement No additional data is available.

  • Correction notice This article has been corrected since it first published. The word 'TEST' has been removed from the first line of the Introduction.

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