Prevalence and main outcomes of placenta accreta spectrum: a systematic review and metaanalysis

OBJECTIVE: 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 DESIGN: Data sources: We searched PubMed, Google Scholar, clinicalTrials.gov and MEDLINE between 1982 and 2018. STUDY ELIGIBILITY CRITERIA: Articles providing data on the number of cases of placenta accreta spectrum per pregnancies, births or deliveries in a defined population. STUDY APPRAISAL AND SYNTHESIS METHODS: Study characteristics were evaluated by two independent reviewers using a predesigned protocol. Primary outcomes were the prevalence of placenta accreta spectrum and clinical diagnostic at birth and pathologic criteria used to confirm the diagnosis. Secondary outcomes included cases requiring transfusion, incidence of peripartum hysterectomy and maternal mortality rates. Heterogeneity between studies was analysed with the Cochran's Q-test and the I2 statistics. RESULTS: Of the 98 full-text studies identified, 29 articles met the defined criteria including 22 retrospective and 7 prospective studies comprising 7,001 cases of placenta accreta spectrum out 5,719,992 births. Prevalence rates ranged between 0.01 and 0.1% with an overall pooled prevalence of 0.17% (95% CI 0.14-0.19). Only 10 studies provided with detailed histopathologic data. The pool prevalence for the adherent versus the invasive grades was 0.5 (95% CI 0.3-0.36) and 0.3 (95% CI 0.2-0.4) per 1000 births, respectively. The pooled incidence for peripartum hysterectomy was 52.2% (95% CI 38.3-66.4; I2= 99.8%) and 46.9% (95 % CI 34-59.9, I2= 98.8%) for haemorrhage requiring transfusion. The pooled estimate of maternal death was 0.05% (95% CI 0.06-0.69, I2=73%). We found large amounts of heterogeneity between studies for all parameters and further quantifying was limited because of methodological inconsistencies between studies with regards to clinical criteria 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. CONCLUSIONS: This meta-analysis indicates wide variation between studies for the prevalence rate of placenta accreta spectrum and for the different grades of accreta placentation, highlighting the need for consistency in definitions used to describe placenta accreta spectrum at birth and in reporting on this increasing common obstetric complication

Epidemiology of placenta previa accreta: a systematic review and meta-analysis

Objective To estimate the prevalence and incidence of placenta previa complicated by placenta accreta spectrum (PAS) and to examine the different criteria being used for the diagnosis. Design Systematic review and meta-analysis. Data sources PubMed, Google Scholar, ClinicalTrials.gov and MEDLINE were searched between August 1982 and September 2018. Eligibility criteria Studies reporting on placenta previa complicated by PAS diagnosed in a defined obstetric population. Data extraction and synthesis Two independent reviewers performed the data extraction using a predefined protocol and assessed the risk of bias using the Newcastle-Ottawa scale for observational studies, with difference agreed by consensus. The primary outcomes were overall prevalence of placenta previa, incidence of PAS according to the type of placenta previa and the reported clinical outcomes, including the number of peripartum hysterectomies and direct maternal mortality. The secondary outcomes included the criteria used for the prenatal ultrasound diagnosis of placenta previa and the criteria used to diagnose and grade PAS at birth. Results A total of 258 articles were reviewed and 13 retrospective and 7 prospective studies were included in the analysis, which reported on 587 women with placenta previa and PAS. The meta-analysis indicated a significant (p<0.001) heterogeneity between study estimates for the prevalence of placenta previa, the prevalence of placenta previa with PAS and the incidence of PAS in the placenta previa cohort. The median prevalence of placenta previa was 0.56% (IQR 0.39–1.24) whereas the median prevalence of placenta previa with PAS was 0.07% (IQR 0.05–0.16). The incidence of PAS in women with a placenta previa was 11.10% (IQR 7.65–17.35). Conclusions The high heterogeneity in qualitative and diagnostic data between studies emphasises the need to implement standardised protocols for the diagnoses of both placenta previa and PAS, including the type of placenta previa and grade of villous invasiveness. PROSPERO registration number CRD4201706858