Preeclampsia is the main cause of maternal and perinatal death. Multiple studies suggest that trace elements were associated with preeclampsia, but the results varied, and less known about early or mid-term pregnancy of trace elements and preeclampsia. We aim to explore the association between mid-term pregnancy trace elements levels and preeclampsia.The retrospective cohort study was consecutively conducted in Foshan Fosun Chancheng Hospital, Guangdong Province, China, from August 1, 2019, to November 30, 2019. Trace elements are derived from the laboratory data system, measured in maternal whole blood during 12-27 (+6) weeks of pregnancy by flame atomic absorption spectrometer method. Preeclampsia diagnosis and covariance were ascertained from the electronic medical records system. We used multivariable logical regression to estimate odds ratios (OR) and 95% CIs.A total of 2186 participants were included in this study, and 59 (2.70%) women developed preeclampsia. After multivariable adjustment, the OR of Mg levels for preeclampsia was 0.35 (95%CI:0.06,2.20). The fifth quintiles of Mg were associated with 0.29 (95% CI：0.10,0.85) times lower risk of preeclampsia compared with the first quintile, with a dose-response trend (P for trend = 0.056). Per 1 µmol/L increment in Cu was associated with 11% lower risk of preeclampsia (OR=0.89; 95% CI, 0.78,1.02). Compared with the first quintile, the second, third，fourth，fifth quintile of Cu was associated with a odd ratio of 0.12 (95% CI:0.03,0.43),0.67 (95% CI:0.30,1.48),0.33 (95% CI:0.15,0.76) and 0.26 (95% CI:0.10,0.66),respectively. Null associations were observed for Zn, Fe, Ca.Higher blood Mg and Cu levels in mid-term pregnancy were associated with lower preeclampsia risk.Copyright © 2022 The Authors. Published by Elsevier GmbH.. All rights reserved.