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Incidence, risk factors and perinatal outcomes for placenta accreta in Australia and New Zealand: a case–control study
  1. Cynthia M Farquhar1,
  2. Zhuoyang Li2,
  3. Sarah Lensen1,
  4. Claire McLintock3,
  5. Wendy Pollock4,
  6. Michael J Peek5,
  7. David Ellwood6,
  8. Marian Knight7,
  9. Caroline SE Homer2,
  10. Geraldine Vaughan2,
  11. Alex Wang2,
  12. Elizabeth Sullivan2
  1. 1 Department of Obstetrics and Gynaecology, University of Auckland, Auckland, New Zealand
  2. 2 Australian Centre for Public and Population Health Research, Faculty of Health, University of Technology Sydney, Sydney, New South Wales, Australia
  3. 3 Department of National Women’s Health, Auckland City Hospital, Auckland, New Zealand
  4. 4 Department of Nursing, Melbourne School of Health Sciences, The University of Melbourne and School of Nursing and Midwifery, Melbourne, Australia
  5. 5 Department of ANU Medical School, Australian National University, Canberra, Australia
  6. 6 School of Medicine, Griffith University, Gold Coast, Queensland, Australia
  7. 7 National Perinatal Epidemiology Unit, Oxford, UK
  1. Correspondence to and Dr Cynthia M Farquhar; c.farquhar{at}


Objective Estimate the incidence of placenta accreta and describe risk factors, clinical practice and perinatal outcomes.

Design Case–control study.

Setting Sites in Australia and New Zealand with at least 50 births per year.

Participants Cases were women giving birth (≥20 weeks or fetus ≥400 g) who were diagnosed with placenta accreta by antenatal imaging, at operation or by pathology specimens between 2010 and 2012. Controls were two births immediately prior to a case. A total of 295 cases were included and 570 controls.

Methods Data were collected using the Australasian Maternity Outcomes Surveillance System.

Primary and secondary outcome measures Incidence, risk factors (eg, prior caesarean section (CS), maternal age) and clinical outcomes of placenta accreta (eg CS, hysterectomy and death).

Results The incidence of placenta accreta was 44.2/100 000 women giving birth (95% CI 39.4 to 49.5); however, this may overestimated due to the case definition used. In primiparous women, an increased odds of placenta accreta was observed in older women (adjusted OR (AOR) women≥40 vs <30: 19.1, 95% CI 4.6 to 80.3) and current multiple birth (AOR: 6.1, 95% CI 1.1 to 34.1). In multiparous women, independent risk factors were prior CS (AOR ≥2 prior sections vs 0: 13.8, 95% CI 7.4 to 26.1) and current placenta praevia (AOR: 36.3, 95% CI 14.0 to 93.7). There were two maternal deaths (case fatality rate 0.7%).

Women with placenta accreta were more likely to have a caesarean section (AOR: 4.6, 95% CI 2.7 to 7.6) to be admitted to the intensive care unit (ICU)/high dependency unit (AOR: 46.1, 95% CI 22.3 to 95.4) and to have a hysterectomy (AOR: 209.0, 95% CI 19.9 to 875.0). Babies born to women with placenta accreta were more likely to be preterm, be admitted to neonatal ICU and require resuscitation.

  • caesarean
  • c-section
  • placenta accreta
  • placentation

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  • Contributors CF, MP, ES, CM, WP, DE, MK and CH conceptualised and designed the study protocol and case report forms. GV and ES managed data collection and oversaw operational aspects of the study. SL, ZL, ES and CF devised the data analysis. ZL, AW undertook the data analysis. CF, SL, ES and ZL led the drafting of the paper. All authors revised the manuscript and approved the final draft.

  • Funding This work was supported by the National Health and Medical Research Council (App ID 510298) from 2008 to 2012 in Australia and the Perinatal and Maternal Mortality Review Committee in New Zealand. The funding sources had no involvement in the study design, conduct, analysis, manuscript drafting or decision to publish.

  • Competing interests All authors have completed the ICMJE uniform disclosure form at and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethics approval NSW Population and Health Services Research Ethics Committee.

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

  • Data sharing statement Unpublished data are not available.

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