3 Evaluation of a More Restrictive, Heparin-Based, Obstetric Thromboprophylaxis Protocol

In 2016 our institution adopted VTE prophylaxis guidelines based on ACOG recommendations. These guidelines recommended heparin-based chemoprophylaxis for those with ≥ 2 VTE risk factors (e.g. obesity, chorioamnionitis, preeclampsia). As institutional data showed increased wound hematomas and no difference in VTEs, we adopted a more restricted approach requiring ≥ 3 risk factors with fewer conditions considered risk factors (severe preeclampsia vs. all preeclampsia). Our objective was to evaluate outcomes after the implementation of this revised, more restrictive obstetric thromboprophylaxis protocol. Retrospective cohort study of patients who delivered at our institution between January 1, 2016 and December 31, 2018 (original guidelines) and between December 1, 2021 and May 31, 2023 (revised guidelines). High-risk patients (thrombophilia, prior/current VTE) on antepartum anticoagulation were excluded. Our primary outcome was clinical diagnosis of wound hematoma up to 6 weeks postpartum. Secondary outcome was new diagnosis of postpartum VTE. We compared baseline characteristics and outcomes between groups and estimated adjusted odds ratios (aOR) with 95% confidence intervals (CI) of primary and secondary outcomes using the original guideline group as reference. Of 17,489 patients included in our analysis, 12,430 (71%) were in the original guidelines group, and 5,029 (29%) in the revised group. Rates of chemoprophylaxis decreased by 50% - from 16% during the original guidelines to 8% after revision. Groups differed in baseline characteristics including age, race, insurance status, and comorbidities. Compared to the original guidelines, more restrictive guidelines were associated with a > 50% significant decrease in any wound hematoma (0.7% vs. 0.3%, aOR 0.38, [0.21-0.67]), specifically due to a 50% reduction in superficial wound hematomas (0.6% vs. 0.3%, aOR 0.43 [0.24-0.75]). There was no increase in VTE, DVT, or PTE (Figure). A more conservative approach to VTE prophylaxis decreased rates of wound hematomas without an increase in postpartum VTE.