This study aimed to compare the levels of sialic acid (SA) in saliva during pregnancy between groups of women with preeclampsia (PE) without severity criteria and with severity criteria. 60 pregnant women diagnosed with PE were studied in total. The patients were divided into two groups: 30 women with PE without severity criteria (PEOS) and 30 women with PE diagnosis with severity criteria (PEWS). Salivary SA levels were determined using surface-enhanced Raman spectroscopy (SERS), and citrate-covered silver nanoparticles as an amplifying substrate. The mean SA concentrations of PEOS and PEWS patients were 34 ± 15.6 vs 75 ± 22 mg/dL, respectively. Participants with severity criteria had more than twice the median SA levels as those without severity criteria, as determined by the SERS-calibrated technique. Our results indicate that SA determination from saliva using SERS may become a very effective, rapid, and cost-effective diagnostic tool for PE severity.