Antithrombotic prophylaxis during pregnancy in women with deficiency of natural anticoagulants.

Prevalence of obstetric complications in women with deficiency of natural anticoagulants is difficult, because these defects are very rare in general population. Furthermore, the available data on prophylactic intervention in such individuals to decrease the obstetric risk are also very limited. To evaluate in a setting of women with rare hereditary thrombophilias, deficiency of antithrombin, protein C or protein S whether thromboprophylaxis during pregnancy could affect foeto-maternal outcome. Retrospective cohort study in two Italian thrombosis centres: 32 women with an established hereditary deficiency of natural anticoagulants antithrombin, protein C or protein S were enrolled because of a history of unexplained foetal losses with or without venous thromboembolism. Overall, information on the management of 103 pregnancies was obtained and the outcome in the absence or in the presence of enoxaparin treatment was recorded. Live births were recorded in 18 women (56.2%). Ten women had early foetal losses, 16 intrauterine foetal death and six both. Eight pregnancies were treated with enoxaparin. Seven out of eight treated pregnancies [87.5%, 95% confidence interval (CI) 52.9-97.7] and 27 out of 95 not-treated pregnancies (28.4%, 95% CI 20.3-38.1) resulted in the delivery of a live newborn (Fisher exact test: P=0.002), with a risk of foetal loss in untreated pregnancies 3.1 times (95% CI 1.7-3.5) higher than in treated ones. In this setting of patients with rare causes of thrombophilia, antithrombotic prophylaxis during pregnancy improves foeto-maternal outcome.