RESUMO
OBJECTIVES: To examine the outcomes of planned induction of labour versus spontaneous onset of labour among women using prophylactic-dose low-molecular weight heparin (LMWH) therapy. DESIGN: Retrospective cohort study. SETTING: University hospital. POPULATION: Women receiving 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 anaesthesia. RESULTS: Data from 199 women were analysed; 78 (39.2%) were admitted following spontaneous onset of labour and 121 (60.8%) underwent planned induction of labour. Compared to women who underwent planned induction of labour, women who presented with spontaneous onset of labour had a shorter median admission-to-delivery interval (4.7 versus 29.3 hours, P < 0.001). Similarly, intervals from the last LMWH injection to delivery (25.8 versus 48.2 hours, P < 0.001) and to the first postpartum LMWH injection (41.2 versus 63.7 hours, P < 0.001) were shorter. Among those with spontaneous onset of labour, 69 (88.5%) were eligible to receive neuraxial anaesthesia. Rates of postpartum haemorrhage and blood transfusion were similar between the groups. No thrombotic events were encountered in those with spontaneous onset of labour, but four (3.3%) women who delivered following induction of labour developed a postpartum thrombotic event. CONCLUSION: Planned induction of labour was associated with a higher risk of postpartum thrombotic events than was spontaneous onset of labour (4 of 121 [3.3%] versus 0 of 78 [0%]), presumably due to prolonged duration of anticoagulation interruption, although the difference was not statistically significant. Allowing spontaneous onset of labour was associated with comparable rates of bleeding complications, and only a low proportion (9 of 78, 11.5%) were not eligible to receive neuraxial anaesthesia. TWEETABLE ABSTRACT: Planned induction among women using prophylactic LMWH therapy might increase the risk of thromboembolic complications.