Background: The aim of this study was to evaluate the relationship and impact of D-dimer levels and preeclamptic pregnancies at different ages in women. Methods: We conducted an observational retrospective cohort study of 325 pregnant women who delivered in Wenzhou People’s Hospital from January 2018 to December 2021. Clinical data including age, neutrophils, lymphocytes, platelets, fibrinogen, gestational age, D-dimer/fibrinogen, blood pressure at admission, and fetal weight were collected from the medical record database. All measurements were made using the same methods. Data for continuous variables were expressed as X \pm standard deviation (SD), and inter-group differences in continuous data were compared by independent sample t-test. Continuous variables that do not conform to the normal distribution, such as age and D-dimer, were expressed as median and quartile ranges. The relationship between D-dimer and preeclampsia pregnant women of different ages was evaluated by receiver operating characteristics (ROC) curve analysis. Results: Among the middle-aged pregnant women, the average D-dimer in the normotensive pregnancy group was (1.367 \pm 0.03 mg/L), which was significantly lower than that in the preeclampsia group (2.087 \pm 0.16 mg/L). The D-dimer/fibrinogen ratio was comparable between the young groups, but there was a difference between the middle-aged groups. Meanwhile, in middle-aged pregnant women, the predicted area of D-dimer for preeclampsia was 70.2% (95% confidence interval (CI) 60–80.43%, p = 0.0002) , which was significantly higher than that in the young group. Conclusions: Prenatal D-dimer levels may be associated with more accurate predictors of preeclampsia in middle-aged women than in young women.