Planned induction versus spontaneous delivery among women using prophylactic anticoagulation therapy: a retrospective study

OBJECTIVES: To examine the outcomes of planned induction of labor versus spontaneous onset of labor among women using prophylactic-dose low-molecular weight heparin (LMWH) therapy. DESIGN: Retrospective cohort study. SETTING: University hospital. POPULATION: Women under antepartum prophylactic LMWH therapy undergoing a trial of vaginal delivery. METHODS: Charts from 2018-2019 were reviewed. MAIN OUTCOME MEASURES: Duration of anticoagulation interruption and eligibility to receive neuraxial anesthesia. RESULTS: Data from 199 women were analyzed; 78 (39.2%) were admitted following spontaneous onset of labor and 121 (60.8%) underwent planned induction of labor. Compared to women who underwent planned induction of labor, women who presented with spontaneous onset of labor had a shorter median admission-to-delivery interval (4.7 vs. 29.3 hours,P<0.001). Similarly, intervals from the last LMWH injection to delivery (25.8 vs. 48.2 hours,P<0.001) and to the first postpartum LMWH injection (41.2 vs. 63.7 hours,P<0.001) were shorter. Among those with spontaneous onset of labor, 69 (88.5%) were eligible to receive neuraxial anesthesia. Rates of postpartum hemorrhage and blood transfusion were similar between the groups. While no thrombotic events were encountered in those with spontaneous onset of labor, four (3.3%) women who delivered following induction of labor developed a postpartum thrombotic event. CONCLUSION: Planned induction of labor was associated with a higher risk of postpartum thrombotic events than with spontaneous onset of labor (4 of 121 (3.3%) vs. 0 of 78 (0%))presumably due to prolonged duration of anticoagulation interruption, although the difference was not statistically significant. Allowing spontaneous onset of labor was associated with comparable rates of bleeding complications, and only a low proportion (9 of 78, 11.5%) were not eligible to receive neuraxial anesthesia.