- Objective: To examine the association between calcium levels during the first trimester of pregnancy and preeclampsia. Methods: The study population included registered births (n = 5233) in a tertiary medical center between 2001 and 2011. A comparison was performed between women with and without hypocalcemia during the first trimester of pregnancy. A second analysis was performed after correcting calcium levels for albumin. Multiple logistic regression models were used to control for confounders. Receiver operating characteristic curve analysis graphs were used to describe the relationship between the true-positive rate (sensitivity) and the false-positive rate for different values of calcium during the first half of pregnancy in the prediction of preeclampsia. Results: Of 5233 deliveries, 841 (16%) had hypocalcemia and 4392 (84%) had a normal calcium level. No significant difference were found between the groups regarding mild preeclampsia [odds ratio (OR) = 1.216; 95% confidence interval (CI) 0.831-1.779; p = 0.312], severe preeclampsia (OR = 1.618; 95% CI 0.919-2.849; p = 0.092) and any hypertensive disorders (OR = 1.324; 95% CI 0.963-1.821; p = 0.083). Conclusions: Hypocalcemia during the first trimester of pregnancy is not a risk factor for preeclampsia.