Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): Dazhi Fan, Qing Xia, Li Liu, Shuzhen Wu, Guo Tian, Wen Wang, Song Wu, Xiaoling Guo, Zhengping Liu, Cassandra Nichole Spracklen.
The global burden of postpartum hemorrhage (PPH) in women with placenta previa is a major public health concern. Although there are different reports on the incidence of PPH in different countries, to date, no research has reviewed them.
The aim of this study was to calculate the average point incidence of PPH in women with placenta previa.
A systematic review and meta-analysis of observational studies estimating PPH in women with placenta previa was conducted through literature searches in four databases in Jul 2016. This study was totally conducted according to the MOOSE guidelines and in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses standard.
From 1148 obtained studies, 11 included in the meta-analysis, which involved 5146 unique pregnant women with placenta previa. The overall pooled incidence of PPH was 22.3% (95% CI 15.8–28.7%). In the subgroup, the prevalence was 27.4% in placenta previas, and was 14.5% in low-lying placenta previa; the highest prevalence was estimated in Northern America (26.3%, 95%CI 11.0–41.6%), followed by the Asia (20.7%, 95%CI 12.8–28.6%), Australia (19.2%, 95% CI 17.2–21.1%) and Europe (17.8%, 95% CI, 11.5%-24.0%).
The summary estimate of the incidence of PPH among women with placenta previa was considerable in this systematic review. The results will be crucial in prevention, treatment, and identification of PPH among pregnant women with placenta previa and will be contributed to the planning and implantation of relevant public health strategies.
Placenta previa (PP) is characterized by the abnormal placenta overlying the endocervical os, and it is known as one of the most feared adverse maternal and fetal-neonatal complications in obstetrics [1, 2]. All placentas overlying the os (to any degree) are termed previas and those near to but not overlying the os are termed low-lying . There appears to be an association between endometrial damage and uterine scarring and subsequent placenta previa . Meanwhile, the condition is frequently complicated by invasion of placental villi beyond the decidua basalis causing placenta accreta or increta . Placenta increta can unexpectedly lead to catastrophic blood loss, multiple complications, and even death . Thus, women with placenta previa have often increased the risk of postpartum hemorrhage (PPH).
This systematic review was conducted according to the MOOSE guidelines  and in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standard . Supporting information showed the protocol and checklist (S1 Protocol and S1 Checklist).
The aim of this systematic review and meta-analysis is to study the present status of the incidence of postpartum hemorrhage (PPH) in pregnant women with placenta previa (PP) and explore the determinants of PPH incidence. To our knowledge, this systematic review is the first meta-analysis and provides a comprehensive overview of the current literature. Based on the data of 11 articles including 14 unique studies, PPH incidence rate (22.3%) remains high, approximately 4-fold higher than among all women, in pregnant women with placenta previa. With reference to types of placenta previa, lower PPH incidence rate was demonstrated in low-lying placenta pregnant women (14.5%). When evaluated by study region, the incidence was high in North America (26.3%), intermediate in Asia (20.7%) and Australia (19.2%) and low in Europe (17.8%). In addition, it was also found that prior cesarean section associated with increased risk for PPH.