Prior term delivery increases risk of subsequent recurrent preterm birth: An unexpected finding

Natalie Suff*, Vicky X. Xu, Giorgia Dalla Valle, Jenny Carter, Shaun Brennecke, Andrew Shennan

*Corresponding author for this work

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Background: Women with a prior pregnancy at term are generally considered to be at reduced risk for subsequent spontaneous preterm birth (sPTB), whereas a previous sPTB is a major predictor for a future sPTB. Aims: The objective of this study was to investigate the risk of recurrent sPTB in women with a prior term birth and a subsequent sPTB. Materials and Methods: This is a retrospective cohort study conducted at St Thomas’ Hospital in London, UK. There were 430 women included: 230 with a term birth (caesarean section or vaginal delivery) preceding a sPTB (term + sPTB group) and 200 with a prior sPTB only (sPTB only group). The primary outcome was sPTB, <37 weeks gestation. Results: Of the term + sPTB group, 38.7% (89/230) had a recurrent sPTB compared to 20% (40/200) in the sPTB only group (P < 0.0001), with a relative risk (RR) of 1.9. Of women who had a term caesarean section and a subsequent PTB, 50% (30/60) had a further sPTB (RR 2.5 compared to the sPTB only group), while 34.7% (59/170) of women who had a term vaginal birth and subsequent sPTB, had a further sPTB (RR 1.7 compared to the sPTB only group). Conclusion: In women who have had a previous sPTB, the risk of a recurrence is much higher than in women with a prior term birth. The aetiology of PTB may be different in this subgroup of women and needs to be further elucidated to determine how best to identify and treat them.

Original languageEnglish
Pages (from-to)500-505
Number of pages6
JournalAustralian and New Zealand Journal of Obstetrics and Gynaecology
Issue number4
Early online date27 Feb 2022
Publication statusPublished - Aug 2022


  • caesarean section
  • late miscarriage
  • obstetrics
  • preterm birth


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