Systematic Reviews
Prevalence and main outcomes of placenta accreta spectrum: a systematic review and meta-analysis

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Objective Data

The objective of this study was to evaluate the prevalence of placenta accreta spectrum in general population studies and the main maternal outcomes at delivery.

Study

We searched PubMed, Google Scholar, clinicalTrials.gov, and MEDLINE between 1982 and 2018. Articles that provided data on the number of cases of placenta accreta spectrum per pregnancies, births, or deliveries in a defined population were used.

Study Appraisal and Synthesis Methods

Study characteristics were evaluated by 2 independent reviewers who used a predesigned protocol. Primary outcomes were the prevalence of placenta accreta spectrum and clinical diagnostic data at birth; the pathologic criteria were used to confirm the diagnosis. Secondary outcomes included cases that required transfusion, incidence of peripartum hysterectomy, and maternal mortality rates. Heterogeneity between studies was analyzed with the Cochran’s Q-test and the I2 statistics.

Results

Of the 98 full-text studies that were identified, 29 articles met the defined criteria and included 22 retrospective and 7 prospective studies comprising 7001 cases of placenta accreta spectrum of 5,719,992 births. Prevalence rates ranged from 0.01–1.1% with an overall pooled prevalence of 0.17% (95% confidence interval, 0.14–0.19). Only 10 studies provided detailed histopathologic data. The pool prevalence for the adherent vs the invasive grades was 0.5 (95% confidence interval, 0.3–0.36) and 0.3 (95% confidence interval, 0.2–0.4) per 1000 births, respectively. The pooled incidence for peripartum hysterectomy was 52.2% (95% confidence interval, 38.3–66.4; I2=99.8%) and 46.9% (95 % confidence interval, 34–59.9; I2=98.8%) for hemorrhage that required transfusion. The pooled estimate of maternal death was 0.05% (95% confidence interval, 0.06–0.69; I2=73%). We found large amounts of heterogeneity between studies for all parameters and further quantification was limited because of methodologic inconsistencies between studies with regards to clinical criteria that were used for the diagnosis of the condition at birth and the histopathologic confirmation of the diagnosis and differential diagnosis between adherent and invasive accreta placentation.

Conclusion

This meta-analysis indicated wide variation between studies for the prevalence rate of placenta accreta spectrum and for the different grades of accreta placentation that highlighted the need for consistency in definitions that are used to describe placenta accreta spectrum at birth and in the reporting of this increasing common obstetric complication.

Section snippets

Eligibility criteria, information sources and search strategy

We undertook a PubMed, Google Scholar, clinicalTrials.gov, and MEDLINE search for studies published in any language between the first prenatal ultrasound description of placenta accreta in July 1982 by Tabsh et al24 and April 1, 2018. The search protocol was designed a priori and registered on PROSPERO (CRD42017068589; www.crd.york.ac.uk/PROSPERO) in line with current recommendations and reported as per PRISMA 2009 guidelines (www. prisma-statement.org). We used MeSH headings, text words, and

Results

From 2170 citations that were identified, we included 29 population studies from 13 different countries for the quantitative analysis (Figure 1).

Principal findings of the study

Our findings have quantified the variability between population studies in the prevalence of placenta accreta spectrum at birth. There was strong evidence of inconsistency between the different types of population studies with regards to the criteria that are used to diagnose and/or confirm the condition at delivery. The meta-analysis found large amounts of heterogeneity for the incidence of peripartum hysterectomy and for hemorrhage that requires transfusion and moderate amounts for maternal

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    No funding was obtained for this study. C.B.’s post is partly funded/supported by the National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy's and St Thomas’ NHS Foundation Trust and King's College London. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, or the Department of Health.

    The authors report no conflict of interest.

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