Determination of normal ranges of shock index and other haemodynamic variables in the immediate postpartum period: A cohort study

Hannah L. Nathan, Kate Cottam, Natasha L. Hezelgrave, Paul T. Seed, Annette Briley, Susan Bewley, Lucy C. Chappell, Andrew H. Shennan

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25 Citations (Scopus)
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Objective To determine the normal ranges of vital signs, including blood pressure (BP), mean arterial pressure (MAP), heart rate (HR) and shock index (SI) (HR/systolic BP), in the immediate postpartum period to inform the development of robust obstetric early warning scores. Study Design We conducted a secondary analysis of a prospective observational cohort study evaluating vital signs collected within one hour following delivery in women with estimated blood loss (EBL) <500ml (316 women) delivering at a UK tertiary centre over a one-year period. Simple and multiple linear regression were used to explore associations of demographic and obstetric factors with SI. Results Median (90% reference range) was 120 (100-145) for systolic BP, 75 (58-90) for diastolic BP, 90 (73-108) for MAP, 81 (61-102) for HR, and 0.66 (0.52-0.89) for SI. Third stage Syntometrine ® administration was associated with a 0.03 decrease in SI (p = 0.035) and epidural use with a 0.05 increase (p = 0.003). No other demographic or obstetric factors were associated with a change in shock index in this cohort. Conclusion This is the first study to determine normal ranges of maternal BP, MAP, HR and SI within one hour of birth, a time of considerable haemodynamic adjustment, with minimal effect of demographic and obstetric factors demonstrated. The lower 90% reference point for systolic BP and upper 90% reference point for HR correspond to triggers used to recognise shock in obstetric practice, as do the upper 90% reference points for systolic and diastolic BP for obstetric hypertensive triggers. The SI upper limit of 0.89 in well postpartum women supports current literature suggesting a threshold of 0.9 as indicating increased risk of adverse outcomes.

Original languageEnglish
Article numbere0168535
Number of pages10
JournalPLoS One
Issue number12
Publication statusPublished - 20 Dec 2016
Externally publishedYes


  • shock index
  • haemodynamics
  • vital signs
  • normal range
  • Postpartum period


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