Venous thromboembolism in pregnancy: prophylaxis and treatment with low molecular weight heparin.

Objective: To evaluate the safety of individually dosed low molecular weight heparin (LMWH) for prophylaxis and treatment of thromboembolic complications in pregnancy.

Design: Cohort study with a chronologic register-based control group.

Setting: Department of Obstetrics and Gynecology, Hillerød Hospital, Denmark.

Population: All 166 women treated with LMWH in pregnancy between 1 January 2001 and 31 December 2005.

Methods: Women treated with LMWH in pregnancy were identified and individual case records reviewed retrospectively. General data on the LMWH-treated women were compared to the 18,020 untreated pregnancies within the same period and with 306 matched controls as regards to postpartum hemorrhage (PPH).

Main Outcome Measures: Side effects of treatment, thromboembolic manifestations, postpartum bleeding and obstetric outcome.

Results: There were no thromboembolic events during therapy, few side effects of treatment and no osteoporotic fractures or episodes of heparin-induced thrombocytopenia. The 166 pregnancies resulted in 159 live infants. There was a significantly higher risk of preterm delivery (13% vs. 6%) and intrauterine growth restriction (4.4% vs. 3.5%). Delivery by cesarean section was more common in these high-risk LMWH-treated pregnancies (33.1%) than in untreated pregnancies (19.2%). In the LMWH-group, the occurrence of PPH was 7.2% compared with 8.8% in the matched untreated control group (p = 0.675). None of the events in the LMWH group were serious and all 166 women were in good health at discharge.

Conclusions: Individually dosed LMWH is well tolerated and safe for prophylaxis and treatment of thromboembolic complications during pregnancy, delivery and the postpartum period.