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Ethnic and socioeconomic variation in cause-specific preterm infant mortality by gestational age at birth: national cohort study
  1. Mary E Kroll1,
  2. Jennifer J Kurinczuk1,
  3. Jennifer Hollowell1,
  4. Alison Macfarlane2,
  5. Yangmei Li1,
  6. Maria A Quigley1
  1. 1 Policy Research Unit in Maternal Health and Care, National Perinatal Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK
  2. 2 Department of Midwifery, School of Health Sciences, City University, London, UK
  1. Correspondence to Professor Maria A Quigley, Policy Research Unit in Maternal Health and Care, National Perinatal Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Oxford OX3 7LF, UK; maria.quigley{at}


Objective To describe ethnic and socioeconomic variation in cause-specific infant mortality of preterm babies by gestational age at birth.

Design National birth cohort study.

Setting England and Wales 2006–2012.

Subjects Singleton live births at 24–36 completed weeks’ gestation (n=256 142).

Outcome measures Adjusted rate ratios for death in infancy by cause (three groups), within categories of gestational age at birth (24–27, 28–31, 32–36 weeks), by baby’s ethnicity (nine groups) or area deprivation score (Index of Multiple Deprivation quintiles).

Results Among 24–27 week births (5% of subjects; 47% of those who died in infancy), all minority ethnic groups had lower risk of immaturity-related death than White British, the lowest rate ratios being 0.63 (95% CI 0.49 to 0.80) for Black Caribbean, 0.74 (0.64 to 0.85) for Black African and 0.75 (0.60 to 0.94) for Indian. Among 32–36 week births, all minority groups had higher risk of death from congenital anomalies than White British, the highest rate ratios being 4.50 (3.78 to 5.37) for Pakistani, 2.89 (2.10 to 3.97) for Bangladeshi and 2.06 (1.59 to 2.68) for Black African; risks of death from congenital anomalies and combined rarer causes (infection, intrapartum conditions, SIDS and unclassified) increased with deprivation, the rate ratios comparing the most with the least deprived quintile being, respectively, 1.54 (1.22 to 1.93) and 2.05 (1.55 to 2.72). There was no evidence of socioeconomic variation in deaths from immaturity-related conditions.

Conclusions Gestation-specific preterm infant mortality shows contrasting ethnic patterns of death from immaturity-related conditions in extremely-preterm babies, and congenital anomalies in moderate/late-preterm babies. Socioeconomic variation derives from congenital anomalies and rarer causes in moderate/late-preterm babies. Future research should examine biological origins of extremely preterm birth.

  • infant mortality
  • premature birth
  • gestational age
  • ethnic groups
  • social class

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  • Contributors JH conceived the study and all authors contributed to the design. Data acquisition was primarily conducted by JH, and data cleaning and management by YL. Analyses were performed by MEK and supported by MAQ and JH. MEK drafted the initial manuscript and JJK, JH, AM and MAQ significantly contributed to revising it.

  • Funding This paper reports on an independent study that is funded by the NIHR Policy Research Programme in the Department of Health and Social Care (grant number 108/001).

  • Disclaimer The views expressed are not necessarily those of the Department.

  • Competing interests None declared.

  • Ethics approval The study was approved by the National Research Ethics Service Committee South Central – Oxford B (reference 15/SC/0493).

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

  • Data sharing statement The Office for National Statistics provided data for this study under an agreement which allows the data to be used only for the programme of infant mortality work of which this is a part.

  • Patient consent for publication Not required.

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