- Objective: The objectives of this study were to determine: 1) longitudinal profile of plasma sST2 concentration of patients with preeclampsia and those with uncomplicated pregnancies; 2) if the changes in sST2 occur prior to the diagnosis of preeclampsia; and 3) the longitudinal profile sST2 of women with early or late preeclampsia. Materials and methods: This longitudinal nested case-control study included singleton pregnancies in the following groups: 1) uncomplicated pregnancies (n = 160); and 2) tjose complicated by early (<34 weeks, n = 9) and late (≥34 weeks, n = 31) preeclampsia. sST2 concentrations were determined by enzyme-linked immunosorbent assay. Mixed-effects models were used for the longitudinal analysis. Results: 1) Plasma sST2 concentration profiles across gestation differed significantly among cases and controls (p < 0.0001); 2) women with early preeclampsia had higher mean sST2 concentrations than controls >22 weeks of gestation; cases with late preeclampsia had higher mean concentrations >33 weeks of gestation (both p < 0.05); and 3) these changes started approximately six weeks prior to clinical diagnosis. Conclusions: Maternal plasma sST2 concentrations are elevated six weeks prior to the clinical diagnosis of preeclampsia. An increase in maternal plasma concentration of sST2 may contribute to an exaggerated intravascular inflammatory response and/or the Th1/Th2 imbalance in some cases.