Background: To evaluate the feasibility of serum microelements, amino acids and acyl carnitine levels to predict maternal complications and adverse infant outcomes in pregnancies complicated by preeclampsia. Methods: We launched a prospective study including 81 pregnant patients. Serum microelements, amino acids and acyl carnitine levels were tested using external calibration technique or high-performance liquid chromatography tandem mass spectrometry. Concentrations of metabolites were compared between the preeclampsia and control groups. Logistic regression models were used to assess the relevance between the metabolites and pregnancy outcomes in preeclampsia patients without severe features. Results: Concentrations of some microelements, amino acids and acyl carnitines were significantly higher or lower in preeclampsia patients. Women with severe preeclampsia had significantly lower (hexadecanoyl carnitine + octadecenoyl carnitine)/acetyl carnitine [(C16 + C18:1)/C2] compared to mothers without severe features. Lower (C16 + C18:1)/C2 was found in women who developed maternal complications (p = 0.07) or experienced adverse infant outcomes (p 0.01) compared with those who did not in patients without severe features. Levels of (C16 + C18:1)/C2 at enrollment resulted in moderate prediction rates for maternal outcomes [areas under the curves (AUC) 0.746, 95% Confidence Interval (CI) 0.543, 0.948] and perinatal outcomes (AUC 0.871, 95% CI 0.729, 1.000). Conclusions: Maternal levels of microelements, amino acids and acyl carnitines were associated with preeclampsia. Levels of (C16 + C18:1)/C2 seemed to be a potential biomarker in the prediction of maternal complications and adverse infant outcomes in preeclampsia patients without severe features. Further studies are needed to validate its predictive application.