Parity and risk of maternal cardiovascular disease: A dose-response meta-analysis of cohort studies

Background Parity has been reported to play an important role in the development of cardiovascular disease; however, the results are still controversial. We aimed to conduct a meta-analysis of cohort studies to assess quantitatively the association between parity and cardiovascular disease risk.Methods PubMed and Web of Science databases were searched to 1 June 2018, supplemented by manual searches of the bibliographies of retrieved articles. And multivariate-adjusted relative risks were pooled by using random-effects models. Restricted cubic spline analysis with four knots was used to explore the relationship of parity and the risk of cardiovascular disease.Results Ten cohort studies involving 150,512 incident cases of cardiovascular disease among 3,089,929 participants were included in the meta-analysis. A significant association between parity and cardiovascular disease risk was observed while comparing parity with nulliparity, with a summarised relative risk of 1.14 (95% confidence interval (CI) 1.09-1.18; I2 = 62.0%, P = 0.002). In the dose-response analysis, we observed a potential non-linear J-shaped dose-response relationship between the number of parity and cardiovascular disease risk, the summary risk estimates for an increase of one live birth was 1.04 (95% CI 1.02-1.05), with significant heterogeneity (I2 = 89.6%). In addition, the similar J-shaped associations between parturition number and cardiovascular disease, ischaemic heart disease or stroke risk were also observed.Conclusions Our findings suggest that ever parity is related to cardiovascular disease risk and there is an association between the number of pregnancies and the risk of cardiovascular disease. Since the number of included studies was limited, further studies are warranted to confirm our findings.