ProblemPreeclampsia (PE) is a serious pregnancy complication leading to high maternal, perinatal morbidity, and mortality. We aimed to investigate the clinical effectiveness of the platelet‐to‐lymphocyte ratio (PLR) in women with PE and compare this measurement to platelet indices as a diagnostic and prognostic marker of PE.Method of studyA total of 471 healthy pregnant women, 126 women diagnosed with mild PE, and 227 with severe PE were included in this retrospective study. We analyzed PLR and platelet indices, mainly mean platelet volume (MPV) and platelet distribution width (PDW) among the 3 groups.ResultsPlatelet distribution width, MPV, and PLR levels in women with PE were significantly different from those of healthy pregnant women. PLR was significantly lower in severe PE than mild PE (P = .001), but PDW and MPV increased as severity of PE progressed; however, the differences in PDW and MPV between women with mild and severe PE were not significant. Receiver operating characteristic curve analysis showed that PLR was more predictive of PE than PDW and MPV (Area under the curve = 0.759 vs 0.621, 0.638). Additionally, the time interval from admission to delivery was significantly shorter in women with PLR‐positive (≤116) than in women with PDW‐positive (>58) and MPV‐positive (>9).ConclusionThe PLR is an easily accessible and cost‐effective parameter, which may be used as a more useful marker for prediction of PE compared to platelet indices. Our study showed that PLR can serve as a useful diagnostic marker of PE.