Association between placenta previa and risk of hypertensive disorders of pregnancy: a meta-analysis based on 7 cohort studies

OBJECTIVE: The aim of this research is to evaluate the association between placenta previa and hypertensive disorders of pregnancy (HDP). MATERIALS AND 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.