Data from: 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. Methods PubMed, Google Scholar, clinicalTrials.gov and
MEDLINE were searched between August 1982 and September 2018 for studies
reporting on placenta previa and placenta previa with PAS diagnosed in a
defined obstetric population. 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 number of peri-partum
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 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). The meta-analysis
indicated a significant level of overall heterogeneity between study
estimates for the prevalence of placenta previa (P<.001), the
prevalence of placenta previa with PAS and the incidence of PAS in the
placenta previa cohort. The high heterogeneity between studies emphasizing
the need to implement standardized protocols for the diagnoses of both
placenta previa and PAS, including the type of placenta previa on
ultrasound imaging and grading of villous invasiveness at delivery.