High serum copper level is associated with an increased risk of preeclampsia in Asians: A meta-analysis

Epidemiological studies evaluating the associations between serum copper and ratios of Cu/Zn and the preeclampsia (PE) risk in Asian population have produced inconsistent results. Therefore, we conducted a meta-analysis to summarize the relationships. We hypothesize that higher serum copper and ratios of Cu/Zn may increase the PE risk. A systematic literature search was performed in PubMed, Web of Science, Embase, Chinese National Knowledge Infrastructure (CNKI), VIP (Database of Chinese Scientific and Technical Periodicals) and Wangfang databases for relevant studies up to November 2016. Pooled standardized mean difference (SMD) was calculated with random effects model. The results showed that PE patients had a higher serum copper level [SMD (95% CI): 1.05 (0.34, 1.77), Z=2.88, P for Z=0.004; I²=96.9%, P for I²<0.0001] compared with healthy pregnancy controls. In subgroup analyses, a higher serum copper level in PE patients was observed in case-control studies [SMD (95% CI): 1.39 (0.44, 2.34)]. No significant difference was found between PE patients and healthy pregnancy controls for ratios of Cu/Zn [(SMD (95% CI): 0.26 (-0.77, 1.29), Z=0.49, P for Z=0.625; I²=95.8%, P for I²<0.0001)]. In conclusion, our meta-analysis indicates that a higher serum copper level is associated with an increased risk of PE. Further studies are needed to confirm these results in future research.