title: Association between placenta previa and risk of hypertensive disorders of pregnancy: a meta-analysis based on 7 cohort studies.
abstract: OBJECTIVE
  The aim of this research is to evaluate the association between placenta previa and hypertensive disorders of pregnancy (HDP).
  
  
  METHODS
  A computerized literature search was carried out on PubMed to collect relevant articles on the association between placenta previa and HDP before November 2013. Pooled relative risk (RR) and 95% confidence intervals (CIs) were used to assess the strength of the associations.
  
  
  RESULTS
  A total of 7 cohort studies were identified according to the inclusion criteria. Overall, a significantly inverse correlation between placenta previa and HDP was found when all study results were pooled into the meta-analysis (RR = 0.55, 95% CI: 0.32-0.97). For subgroup analyses, the same results were found in pregnancy-induced hypertension (PIH) group (RR = 0.36, 95% CI: 0.23-0.57) but not in other HDPs group (RR = 0.94, 95% CI: 0.44-2.00).
  
  
  CONCLUSIONS
  This meta-analysis suggested a reduced risk for PIH in women with placenta previa.
authors.affiliation: Center of Reproductive Medicine, Affiliated Provincial Hospital of Anhui Medical University, Hefei, Anhui, China. xuaiyin2014@126.com.
authors.forename: X-A
authors.initials: XA
authors.lastname: Yin
authors.forename: Y-S
authors.initials: YS
authors.lastname: Liu
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000453:epidemiology; D010923:Placenta Previa / Q000175:diagnosis* / Q000453:epidemiology*; D011225:Pre-Eclampsia / Q000175:diagnosis* / Q000453:epidemiology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis / Q000453:epidemiology; D012307:Risk Factors