Labor characteristics and Perinatal Outcomes Associated with Low Molecular Weight Heparin Therapy: Differential Effects in Induced versus Spontaneous Labor

Objective: To evaluate the effects of long-term low molecular weight heparin (LMWH) use during pregnancy on labor process and pregnancy outcomes under different labor onset methods, aiming to inform clinical application strategies. Methods: This retrospective cohort study included parturients from November 2020 to November 2024. Subjects were grouped based on LMWH exposure and matched using propensity score matching (PSM, 1:2 ratio) for six baseline variables. Subgroup analyses were conducted by labor onset mode (induced vs. spontaneous). Clinical data, pregnancy complications, medications, delivery interventions, and pregnancy outcomes were compared. Multivariate regression analyses were used to assess LMWH’s effects. Results: LMWH use was associated with increased postpartum hemorrhage (PPH) risk (aOR = 2.497, P = 0.032) but reduced CS rates (aOR = 0.617, P = 0.027). In vaginal deliveries, LMWH users showed higher risks of forceps-assisted delivery (aOR = 3.512, P = 0.022) and episiotomy (aOR = 3.059, P = 0.007). In spontaneous labor, LMWH was linked to greater intrapartum blood loss and PPH risk. No significant impact was found on labor duration or neonatal outcomes. Conclusions: Long-term antenatal LMWH use increases PPH and operative vaginal delivery risk, particularly under spontaneous labor. Findings support individualized labor management in LMWH-treated pregnancies.