High serum iron level is associated with an increased risk of hypertensive disorders during pregnancy: a meta-analysis of observational studies

The exact cause of hypertensive disorders in pregnancy (HDP) has not been clearly elucidated. Some researchers have recently investigated the relationship between the serum iron level and the incidence of HDP. However, the results are inconsistent, and these data have not been systematically evaluated. Therefore, we conducted a meta-analysis to evaluate the real association between the serum iron level and the incidence of HDP. We searched for published and ongoing trials in PubMed, EMBASE, Scopus, Web of Science, the Chinese Biomedical Database, CNKI, and the WANFANG database from January 1990 to May 2015 to identify studies that met our predefined criteria. Finally, 26 studies, including 1 cross-sectional study, 23 case-control studies, and 2 prospective nested case-control studies, including 1349 patients and 1119 control participants, were selected for this meta-analysis. The pooled results show that a high serum iron level increased the incidence of HDP (standard mean deviation [SMD], 1.50; 95% confidence interval [CI], 0.94-2.06; P < .0001), especially gestational hypertension (SMD, 3.65; 95% CI, 1.50-5.81; P = .0009) and preeclampsia (SMD, 1.27; 95% CI, 0.76-1.78; P < .0001). No significant difference was seen between the eclampsia groups and the control participants (SMD, 3.34; 95% CI, −0.02 to 6.69; P = .05). The results of this meta-analysis indicate that a high serum iron level is associated with an increased risk of HDP, especially gestational hypertension and preeclampsia.