Low molecular weight heparin to achieve live birth following unexplained pregnancy loss: a systematic review.

BACKGROUND The management of recurrent pregnancy loss is uncertain. Some cohort studies have identified an association between inherited thrombophilias and recurrent or late non-recurrent pregnancy loss, which has prompted investigators to evaluate the benefit of low molecular weight heparin (LWMH) to achieve live birth. A similar benefit for LMWH has also been proposed independent of thrombophilia status. OBJECTIVE AND METHODS We conducted a systematic review of randomized controlled trials to assess the benefit of LMWH in achieving live birth for women with a history of recurrent or late non-recurrent pregnancy loss in the absence of antiphospholipid antibodies. RESULTS For the five studies that satisfied the eligibility criteria, the risk ratio of live birth for women with a history of pregnancy loss treated with LWMH compared with control ranged from 0.95 to 3.00. There was considerable heterogeneity among studies in terms of treatment effect (Q-value was 41.7, P=0.000, and I2=90.4%) independent of thrombophilia status. There was also a wide variation among all studies in terms of definition of early or late pregnancy loss, thrombophilic risk factors, and number of prior pregnancy losses. CONCLUSION There is a trend for increased live births when using LWMH for the prevention of recurrent pregnancy loss. Currently, there is insufficient evidence to support the routine use of LWMH to improve pregnancy outcomes in women with a history of pregnancy loss. Not only are additional studies necessary but standardized criteria for trials evaluating the benefit of an intervention in recurrent pregnancy loss should be established.