Objective: The aim of this study was to determine the correlation between trombocytes volume and severity of the disease on pregnants who diagnosed mild, severe preeclampsia or eclampsia. Methods: In this study 58 pregnants whose ages between 17 and 41 and past 28th week of delivery were included in this study. Twenty healthy pregnants were in control group (Group K) and 38 preeclamptic pregnants were in study group. Study group was seperated into two groups as 20 mild preeclamptic pregnants (Group H) and 18 severe preeclamptic pregnants (Group A). Furthermore, thrombocyte counts were seperated into 3 groups as <100,000/mm3 (Group 1), 100,000-150,000/mm3 (Group 2), >150,000/mm3 (Group 3) and association between thrombocyte volumes and thrombocyte counts were determined. Complete cell count was viewed for two times at 3rd trimester and 6 weeks after delivery and mean thrombocyte volumes and thrombocyte counts were recorded at this time. Association between mean thrombocyte volumes on severity of preeclampsia and thrombocyte counts were examined. Demographic characteristics, number of births, week of pregnancy, birthweight, type of delivery and fetal biometric measurements were recorded. Results: Prenatal and postnatal mean thrombocyte volumes of Group A was found higher than Group H and Group K. Comparison of prenatal and postnatal mean thrombocyte volumes of Group K and Group H were found insignificant. Prenatal thrombocyte counts were seperated into three groups as <100,000/mm3 (Group 1), 100,000-150,000/mm3 (Group 2), >150,000/mm3 (Group 3), mean thrombocyte volumes of groups were calculated 10.11±0.72 fl (femtoliter), 18±0.48 fl, 7.82±0.53 fl, respectively. According to MPV values, comparison between 2. group and 3. group were found insignificant, however comparison between 1. group and 2. group with 3. group were found significant. As a result of these examinations, mean thrombocyte volume was increasing if the clinical situation was gone worse and thrombocyte count was dropped Conclusion: Nearby prognostic factors, MPV values may be usefull for seriousness of preeclampsia. But if the literature is examined, increased MPV values are found at normal pregnancies. These parameters can be usefull for Preeclampsia follow up but more studies is neeeded. [ABSTRACT FROM AUTHOR]