BACKGROUND: Pregnancy in SLE continues to be a challenge. The neutrophil-to-lymphocyte ratio (NLR) and chemerin are predictors of preeclampsia in the general population; however, their role as predictors of maternal-fetal complications in pregnant SLE patients has not been analyzed. OBJECTIVE: To investigate the prognostic value of NLR and serum chemerin, to predict maternal-fetal complications in pregnant SLE patients, and compare both biomarkers among three study groups. METHODS: Design: Analytical cross-sectional study of cases and controls with the following study groups: systemic lupus erythematosus (SLE), preeclampsia, and healthy. NLR and chemerin serum were determined between 20 and 25 weeks of gestation. Patients were evaluated every 4-6 weeks until pregnancy resolution. Maternal and fetal outcomes were registered. We employed Receiver Operating Characteristic (ROC) curves to validate prognostic values. RESULTS: Seventy pregnant patients were included: 20 with SLE, 20 with preeclampsia, and 30 healthy pregnant women; NLR values were 4 (2.3-5.6) in SLE, 6 (4.6-9.2) in preeclampsia, and 2.8 (2.1-2.9) in the group of healthy women (p = .0001). Chemerin levels were: 26 (15.3-56.2) in SLE, 96 (37.3-146.2) in preeclampsia, and 24.6 ng/mL (15.3-47.4) in the healthy group (p = .007) Maternal complications were observed in 11 (55%), 20 (100%), and 8 (26%) per group, respectively. Thrombocytopenia was the most frequent complication in all pregnant women, followed by hypertensive disorders. Fetal complications were registered in 12 (60%), 16 (80%), and 2 (6.7%), respectively. Congenital malformations and prematurity were the most frequent fetal complications. NLR had good diagnostic accuracy in predicting maternal-fetal complications (AUROC 0.715) p = .015, CI 95% 0.56-0.86, cut-off point level: 2.9, sensitivity 61%, specificity 78%, positive predictive value (PPV) 65%, negative predictive value (NPV) 75%. Regarding chemerin, a cut-off point level >43 ng/mL had a sensitivity of 75%, specificity of 72% AUROC 0.75, p = .001, CI 95% 0.61-0.89, PPV 51.7% NPV 87.8%, meaning that 51.7% of patients with chemerin levels >43 ng/mL have or will have preeclampsia. CONCLUSION: The NLR may help predict maternal-fetal complications in SLE pregnancy, constituting a marker of subclinical inflammation. Chemerin levels may be associated with preeclampsia. These biomarkers could improve the care of SLE patients with timely intervention of potential complications during pregnancy.