Background: Combined effects of pregnancy induced hypercoagulability and SARS-CoV-2 infection place pregnant women with COVID-19 disease at high risk of severe outcome. COVID-19 severity has also been associated with serum D-dimer, a biomarker reflecting coagulation and fibrin degradation, in general populations. Despite its prognostic value in pregnant women, the prognostic value of this finding particularly in maternal outcomes remains less understood. The aim of this study was to determine whether elevated serum D-dimer levels in pregnant COVID-19 positive women are of prognostic significance for severe maternal outcomes. Methods: This retrospective observational study included 62 third trimester COVID 19 positive pregnant women admitted to the Department of Obstetrics and Gynecology, BSMMU, Dhaka from March 2019 to February 2020. Serum D-dimer were measured at admission and day 7, 14. D-dimer levels were related to clinical outcomes and statistically evaluated using chi square tests and logistic regression at p < 0.05. Results: Significantly associated with higher risk of severe outcomes, all of which included ICU admission, respiratory complications and adverse pregnancy events is elevated D-dimer levels (≥1.5 mg/L). In logistic regression analysis, patients with D-dimer levels of ≥1.5 mg/L had 3.5-fold greater odds of severe outcomes (OR 3.486; 95% CI, 1.184 to 10.263; p = 0.023). D-dimer had a sensitivity of 64.29%, 67.55% specificity in predicting severe outcomes. Conclusion: Serum D-dimer is valuable prognostic marker of disease severity in pregnant COVID-19 positive women and may be used for early risk assessment and clinical decision making. Routine measurement may help identify early high risk cases in order to improve maternal outcomes.