The Association between Season and Hypertensive Disorders of Pregnancy: A Systematic Review and Meta-Analysis

Background: There is increasing and inconsistent evidence of a relationship between hypertensive disorders of pregnancy (HDP) and season of delivery or conception.Methods: Four databases, the Cochrane Library, PubMed, EMBASE and Web of Science, were searched until September 29th, 2021. Two authors extracted data independently. A random effects model and the Mantel-Haenszel method were used to calculate pooled ORs and 95% CIs.Results: Twenty articles were included in the systematic review, and 11 articles were included in the meta-analysis. The quantitative analysis of the association between delivery season and HDP showed that the odds of HDP was higher in women who deliver in winter than in those who delivered in summer (OR=1.18, 95% CI 1.02-1.38, p < 0.001) and all other seasons (OR = 1.17, 95% CI 1.03-1.34, p