The effect of low molecular weight heparin (dalteparin) on duration and initiation of labour

Abstract

It has recently been reported that women treated with low molecular weight heparin (LMWH) during pregnancy had 3 h shorter duration of delivery. The aim of the present study was to evaluate whether LMWH (dalteparin) affects labour. From January 1996 to December 2005, 217 consecutive pregnancies, out of 34 216 newborn (prevalence 0.6%) that were given thromboprophylaxis with dalteparin (usually 5,000 IU once daily). These 217 consecutive pregnancies were compared to an unselected control group (n = 1,499) of gravidae. Main outcome was time in first and second stage of labour and gestational age at delivery. Among nulliparous women, there were significantly fewer women with prolonged first stage of labour as compared to controls (4.1% vs. 8.5%, P = 0.047). In addition, the duration of first stage of labour was 1 h shorter among those treated with LMWH (5.2 vs. 6.2 h, P = 0.06). There were no such differences among parous women. The risk of prematurity, profuse blood loss, and postpartum anaemia was almost doubled among those treated with LMWH (11.5% vs. 5.9%, P = 0.002, 10.6% vs. 5.9%, P < 0.001, and 12.9% vs. 8.7%, P = 0.048, respectively). Treatment with a prophylactic dose of LMWH (dalteparin) during pregnancy was related to fewer women with prolonged first stage of labour, but also to an increased risk of prematurity and blood loss complications.

Does Use of Low-Molecular-Weight Heparin during Pregnancy Influence the Risk of Prolonged Labor: A Population-Based Cohort Study

“…To our knowledge, the effect of LMWH on duration of labor has only been investigated in two clinical studies [ 29 , 30 ]. Isma et al found that 104 nulliparous women exposed to the LMWH dalteparin had, compared to 787 untreated women, one hour shorter first stage of labor and a significantly lower risk of prolonged first stage of labor (4.1% vs 8.5%, respectively P = 0.047).…”

“…Isma et al found that 104 nulliparous women exposed to the LMWH dalteparin had, compared to 787 untreated women, one hour shorter first stage of labor and a significantly lower risk of prolonged first stage of labor (4.1% vs 8.5%, respectively P = 0.047). No such relationships were found for parous women [ 29 ]. One of the main differences with our study is that we examined the diagnosis of labor dystocia and not the actual duration of labor.…”

“…Further, in the study by Isma et al, there were significant differences for confounders as maternal age, maternal weight, epidural analgesia, gestational length at delivery and frequency of preterm deliveries in the exposed and unexposed groups. This was not accounted for in the analysis and may partly explain the shorter duration of labor among women with use of LMWH [ 29 ].…”

“…Systematic reviews have demonstrated the safety of LMWH, which neither cross the placenta, nor pass to breast milk [ 13 , 28 ]. There is less known about obstetric outcomes and complications; most studies are small and show contradictory results regarding risks of preterm delivery, fetal growth restriction, bleeding complications and cesarean section [ 11 , 29 – 36 ]. Two studies have demonstrated a shorter duration of labor for nulliparous women treated with the LMWH dalteparin and a reduced risk of prolonged first stage of labor [ 29 , 30 ].…”

Efficacy of obstetric thromboprophylaxis and long-term risk of recurrence of venous thromboembolism

“…The corresponding non‐pregnant diagnosis numbers are I269, I801, I803, I808, I822, I823, or I828, and I260, I269. Some of the participants in this study have previously been presented in studies concerning the effect of dalteparin on the duration of labor (17,18). The Ethics Committee at the University of Gothenburg approved the study.…”